Remove glib_compat

[vlasta-labsky]

Fixes #1943

[aquynh]

The original reason was to build Unicorn everywhere, including Windows. Do you try there yet?

[vlasta-labsky]

I haven't tried windows, it may took a while for me to prepare windows build environment (not windows user) ...
It looks that upstream glib supports win builds, so maybe it works just fine.
The issue #1943 that I want to solve is less likely to happen on windows - Qt for windows does not use glib,
and I think there are not many programs/libraries that use glib on windows.
The best option would be to eliminate glib dependency (even the system one) but that it beyond my capabilities.

[wtdcode]

As suggested above, this breaks windows. See CI.

[vlasta-labsky]

I looked at the CI build errors and they are related to missing pkgconfig and/or glib upstream packages - this patch introduces new dependency on upstream glib to replace glib_compat.