Use system allocator for putenv value

The putenv value is stored in environ. If for some reason we
fail to restore it on shutdown, make sure that we fail gracefully
by using a system allocated value, rather than a ZMM allocated one.

This is an additional mitigation for bug #81316 style issues if
all else fails.

Author: nikic

ext/standard/basic_functions.c

@@ -185,7 +185,7 @@ static void php_putenv_destructor(zval *zv) /* {{{ */
 	}
 #endif
 
-	efree(pe->putenv_string);
+	free(pe->putenv_string);
 	efree(pe->key);
 	efree(pe);
 }
@@ -849,7 +849,7 @@ PHP_FUNCTION(putenv)
 		RETURN_THROWS();
 	}
 
-	pe.putenv_string = estrndup(setting, setting_len);
+	pe.putenv_string = zend_strndup(setting, setting_len);
 	pe.key = estrndup(setting, setting_len);
 	if ((p = strchr(pe.key, '='))) {	/* nullify the '=' if there is one */
 		*p = '\0';
@@ -905,7 +905,7 @@ PHP_FUNCTION(putenv)
 		/* valw may be NULL, but the failed conversion still needs to be checked. */
 		if (!keyw || !valw && value) {
 			tsrm_env_unlock();
-			efree(pe.putenv_string);
+			free(pe.putenv_string);
 			efree(pe.key);
 			free(keyw);
 			free(valw);
@@ -939,7 +939,7 @@ PHP_FUNCTION(putenv)
 #endif
 		RETURN_TRUE;
 	} else {
-		efree(pe.putenv_string);
+		free(pe.putenv_string);
 		efree(pe.key);
 #if defined(PHP_WIN32)
 		free(keyw);