Remove mostly obsolete aclocal macros. Make GTK build flags a strict superset
of GLib flags. Use GTK build variables for GTK GUI and GLib elsewhere. Add
dependency flags explicitly instead of using WS_CPPFLAGS.
Some minor improvements and fixes for missing/unnecessary variables (no impact
on our test builds).
Change-Id: I3e1f067a875f79d6516c1fa7af986f17a7a6b671
Reviewed-on: https://code.wireshark.org/review/14005
Reviewed-by: João Valverde <j@v6e.pt>