Deprecate mb_ereg_replace with non-string pattern

I'm counting this towards the non-string needle deprecation from
https://wiki.php.net/rfc/deprecations_php_7_3. I wasn't aware that
mb_ereg_replace() is also affected by this issue. It's even more
ridiculous than usual here, because the integer is interpreted as
an ASCII codepoint, even though these are supposed to be multibyte
functions :(

UPGRADING

@@ -139,6 +139,11 @@ PHP 7.4 UPGRADE NOTES
     so is equivalent to calling a non-static method statically, which has been
     deprecated since PHP 7.0.
 
+- Mbstring:
+  . Passing a non-string pattern to mb_ereg_replace() is deprecated. Currently
+    non-string patterns are interpreted as ASCII codepoints. In PHP 8 the
+    pattern will be interpreted as a string instead.
+
 ========================================
 5. Changed Functions
 ========================================

ext/mbstring/php_mbregex.c

@@ -1049,6 +1049,10 @@ static void _php_mb_regex_ereg_replace_exec(INTERNAL_FUNCTION_PARAMETERS, OnigOp
 		arg_pattern = Z_STRVAL_P(arg_pattern_zval);
 		arg_pattern_len = Z_STRLEN_P(arg_pattern_zval);
 	} else {
+		php_error_docref(NULL, E_DEPRECATED,
+			"Non-string patterns will be interpreted as strings in the future. "
+			"Use an explicit chr() call to preserve the current behavior");
+
 		/* FIXME: this code is not multibyte aware! */
 		convert_to_long_ex(arg_pattern_zval);
 		pat_buf[0] = (char)Z_LVAL_P(arg_pattern_zval);

ext/mbstring/tests/bug72994.phpt

@@ -14,6 +14,8 @@ var_dump($var1);
 --EXPECTF--
 Notice: Undefined variable: var in %s on line %d
 
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
+
 Warning: mb_ereg_replace(): mbregex compile err: invalid code point value in %sbug72994.php on line %d
 bool(false)
 ===DONE===

ext/mbstring/tests/mb_ereg_replace_variation1.phpt

@@ -100,52 +100,82 @@ echo "Done";
 *** Testing mb_ereg_replace() : usage variations ***
 
 -- Iteration 1 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 2 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 3 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 4 --
 
-Warning: mb_ereg_replace(): mbregex compile err: invalid code point value in %smb_ereg_replace_variation1.php on line %d
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
+
+Warning: mb_ereg_replace(): mbregex compile err: invalid code point value in %s on line %d
 bool(false)
 
 -- Iteration 5 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 6 --
 
-Warning: mb_ereg_replace(): mbregex compile err: invalid code point value in %smb_ereg_replace_variation1.php on line %d
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
+
+Warning: mb_ereg_replace(): mbregex compile err: invalid code point value in %s on line %d
 bool(false)
 
 -- Iteration 7 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 8 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 9 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 10 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 11 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 12 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 13 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 14 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 15 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 16 --
@@ -164,11 +194,17 @@ string(10) "string_val"
 string(10) "string_val"
 
 -- Iteration 21 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 22 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 
 -- Iteration 23 --
+
+Deprecated: mb_ereg_replace(): Non-string patterns will be interpreted as strings in the future. Use an explicit chr() call to preserve the current behavior in %s on line %d
 string(10) "string_val"
 Done