gcc: point to our address for bug reports.

As recommended by the FSF in gcc/version.c :

"If you distribute a modified version of GCC, please change
this to refer to a document giving instructions for reporting
bugs to you, not us."

MFC after:	2 weeks

contrib/gcc/version.c

@@ -18,7 +18,7 @@
    forward us bugs reported to you, if you determine that they are
    not bugs in your modifications.)  */
 
-const char bug_report_url[] = "<URL:http://gcc.gnu.org/bugs.html>";
+const char bug_report_url[] = "<URL:http://www.freebsd.org/send-pr.html>";
 
 /* The complete version string, assembled from several pieces.
    BASEVER, DATESTAMP, and DEVPHASE are defined by the Makefile.  */