Description:
------------
if one tries to use the data stream (or any url-based stream), the error message is:

%s:// wrapper is disabled in the server configuration

It would be more helpful if it said:

s:// wrapper is disabled in the server configuration by allow_url_fopen=0

Reproduce code:
---------------
Index: main/streams/streams.c
===================================================================
RCS file: /repository/php-src/main/streams/streams.c,v
retrieving revision 1.82.2.6.2.18.2.1
diff -u -r1.82.2.6.2.18.2.1 streams.c
--- main/streams/streams.c      6 Nov 2007 11:02:36 -0000       1.82.2.6.2.18.2.1
+++ main/streams/streams.c      12 Dec 2007 03:33:09 -0000
@@ -1621,7 +1621,7 @@
                if (options & REPORT_ERRORS) {
                        /* protocol[n] probably isn't '\0' */
                        char *protocol_dup = estrndup(protocol, n);
-                       php_error_docref(NULL TSRMLS_CC, E_WARNING, "%s:// wrapper is disabled in the server configuration", protocol_dup);
+                       php_error_docref(NULL TSRMLS_CC, E_WARNING, "%s:// wrapper is disabled in the server configuration by allow_url_fopen=0", protocol_dup);
                        efree(protocol_dup);
                }
                return NULL;