Drop the custom 'v' format from snprintf custom implementation.

Extensions should instead use the standard 's' format.

Closes GH-5100

Author: Girgias

UPGRADING.INTERNALS

@@ -86,6 +86,9 @@ PHP 8.0 INTERNALS UPGRADE NOTES
      Use the ZEND_LONG_FMT, ZEND_ULONG_FMT and ZEND_XLONG_FMT macros defined in
      php-src/Zend/zend_long.h
 
+     The 'v' format from the custom snprintf implementation has been removed.
+     Use the standard 's' format instead.
+
 ========================
 2. Build system changes
 ========================

main/snprintf.c

@@ -961,7 +961,6 @@ static int format_converter(register buffy * odp, const char *fmt, va_list ap) /
 
 
 				case 's':
-				case 'v':
 					s = va_arg(ap, char *);
 					if (s != NULL) {
 						s_len = strlen(s);