Remove AC_FUNC_VPRINTF

Autoconf 2.59d (released in 2006) 1 started promoting several macros
as not relevant for newer systems anymore, including the AC_FUNC_VPRINTF.

This macro checks for presence of the vprint function otherwise checks
for presence of the _doprnt function. This check was relevant on very
old systems and today can be omitted since it should be well supported
by now. [2]

Also PHP doesn't use the HAVE_VPRINTF or HAVE_DOPRNT symbols.

Refs:
[1] http://git.savannah.gnu.org/cgit/autoconf.git/tree/NEWS
[2] https://www.gnu.org/software/autoconf/manual/autoconf-2.69/autoconf.html

UPGRADING.INTERNALS

@@ -29,6 +29,8 @@ PHP 7.4 INTERNALS UPGRADE NOTES
   a. Unix build system changes
     - configure --help now also outputs --program-suffix and --program-prefix
       information by using the Autoconf AC_ARG_PROGRAM macro.
+    - Obsolescent macro AC_FUNC_VPRINTF has been removed and the HAVE_VPRINTF
+      symbol is no longer defined since it is not needed on current systems.
 
   b. Windows build system changes
 

Zend/Zend.m4

@@ -91,7 +91,6 @@ LIBZEND_CHECK_INT_TYPE(int32_t)
 LIBZEND_CHECK_INT_TYPE(uint32_t)
 
 dnl Checks for library functions.
-AC_FUNC_VPRINTF
 AC_FUNC_MEMCMP
 AC_FUNC_ALLOCA
 AC_CHECK_FUNCS(memcpy strdup getpid kill strtod strtol finite fpclass sigsetjmp)

configure.ac

@@ -596,7 +596,6 @@ AC_CACHE_CHECK([for IPv6 support], ac_cv_ipv6_support,
 dnl Checks for library functions.
 dnl -------------------------------------------------------------------------
 
-AC_FUNC_VPRINTF
 AC_CHECK_FUNCS(
 alphasort \
 asctime_r \

win32/build/config.w32.h.in

@@ -70,7 +70,6 @@
 #undef HAVE_STRUCT_STAT_ST_BLOCKS
 #define HAVE_STRUCT_STAT_ST_RDEV 1
 #define HAVE_UTIME_NULL 1
-#define HAVE_VPRINTF 1
 #define STDC_HEADERS 1
 #define REGEX 1
 #define HSREGEX 1