Bump GLib requirement to 2.76.0
Hi,
This bumps the GLib requirement to 2.76.0 as we are using APIs such as g_set_str()
that were introduced in glib-2.75.1. This will also bump the g-i requirement to 1.76.0 as well as a consequence.
Also, drop the workaround for Visual Studio builds for building against GLib-2.74.x or earlier as 2.76.0 or later is required.
This should fix the vs2017-x64 CI at least.
With blessings, thank you!