There is no reason not to use pkg-config nowadays and this allows to get
rid of some third-party m4 files, which is always nice, and avoids
warnings about GTK 3 and 4 macros being obsolete when regenerating
configure with autoconf 2.71.
This port is not used and is not being worked on, so remove it to reduce the
amount of the code which needs to be updated for every global change.
Also remove tests for VisualAge compiler which isn't used since ages.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76533 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
