ext/curl: Fix CURLOPT_PREREQFUNCTION to not continue on error conditions

This is a follow-up to phpGH-13255.

When the `CURLOPT_PREREQFUNCTION` callback does not return any value
or return an invalid value, we throw a `ValueError` or a `TypeError`
exception. However, it does not prevent the Curl request from going
forward because our default return value is `CURL_PREREQFUNC_OK`.

This changes the default value to `CURL_PREREQFUNC_ABORT`.

Author: Ayesh

ext/curl/interface.c

@@ -722,13 +722,13 @@ static size_t curl_xferinfo(void *clientp, curl_off_t dltotal, curl_off_t dlnow,
 static int curl_prereqfunction(void *clientp, char *conn_primary_ip, char *conn_local_ip, int conn_primary_port, int conn_local_port)
 {
 	php_curl *ch = (php_curl *)clientp;
-	int rval = CURL_PREREQFUNC_OK;
+	int rval = CURL_PREREQFUNC_ABORT;
 
-	// when CURLOPT_PREREQFUNCTION is set to null, curl_prereqfunction still
+	// When CURLOPT_PREREQFUNCTION is set to null, curl_prereqfunction still
 	// gets called. Return CURL_PREREQFUNC_OK immediately in this case to avoid
 	// zend_call_known_fcc() with an uninitialized FCC.
 	if (!ZEND_FCC_INITIALIZED(ch->handlers.prereq)) {
-    	return rval;
+    	return CURL_PREREQFUNC_OK;
     }
 
 #if PHP_CURL_DEBUG