[maintainer update] Doxygen to 1.4.6

Upgrade to bugfix release 1.4.6.
Fixes a crash when using groupdef command under certain circumstances.
http://bugzilla.gnome.org/show_bug.cgi?id=325101

PR: ports/91309
Submitted by: Melvyn Sopacua <mdev@melvyn.homeunix.org>