Use more compact representation for packed arrays.

- for packed arrays we store just an array of zvals without keys.
- the elements of packed array are accessible throuf as ht->arPacked[i]
  instead of ht->arData[i]
- in addition to general ZEND_HASH_FOREACH_* macros, we introduced similar
  familied for packed (ZEND_HASH_PACKED_FORECH_*) and real hashes
  (ZEND_HASH_MAP_FOREACH_*)
- introduced an additional family of macros to access elements of array
  (packed or real hashes) ZEND_ARRAY_ELEMET_SIZE, ZEND_ARRAY_ELEMET_EX,
  ZEND_ARRAY_ELEMET, ZEND_ARRAY_NEXT_ELEMENT, ZEND_ARRAY_PREV_ELEMENT
- zend_hash_minmax() prototype was changed to compare only values

Because of smaller data set, this patch may show performance improvement
on some apps and benchmarks that use packed arrays. (~1% on PHP-Parser)

TODO:
    - sapi/phpdbg needs special support for packed arrays (WATCH_ON_BUCKET).
    - zend_hash_sort_ex() may require converting packed arrays to hash.

main/rfc1867.c

@@ -191,7 +191,7 @@ PHPAPI void destroy_uploaded_files_hash(void) /* {{{ */
 {
 	zval *el;
 
-	ZEND_HASH_FOREACH_VAL(SG(rfc1867_uploaded_files), el) {
+	ZEND_HASH_MAP_FOREACH_VAL(SG(rfc1867_uploaded_files), el) {
 		zend_string *filename = Z_STR_P(el);
 		VCWD_UNLINK(ZSTR_VAL(filename));
 	} ZEND_HASH_FOREACH_END();