bugzilla: remove `gcc-bugs@` mailing list address

bugzilla: remove `gcc-bugs@` mailing list address

Bugzilla is preferred today. Use a URL that gives context about
gathering information prior to actually filing a bug at Bugzilla.

ChangeLog:

	* config-ml.in: Replace gcc-bugs@ with bug reporting link.
	* symlink-tree: Replace gcc-bugs@ with bug reporting link.

fixincludes/ChangeLog:

	* README: Replace gcc-bugs@ with bug reporting link.

gcc/testsuite/ChangeLog:

	* lib/file-format.exp: Replace gcc-bugs@ with bug reporting link.

libcpp/ChangeLog:

	* configure: Regenerate.
	* configure.ac: Replace gcc-bugs@ with bug reporting link.

libdecnumber/ChangeLog:

	* configure: Regenerate.
	* configure.ac: Replace gcc-bugs@ with bug reporting link.