build: Bump GLib minimum required to 2.44
This is required by g_strv_contains(), and xfce4-dev-tools >= 4.17.1 set GLIB_VERSION_MAX_ALLOWED to the GLib version found in configure.ac.in. This usually only generates deprecation warnings, but in some cases it changes the code path used at compile time and can cause memory corruption and crash.
Related: apps/xfburn#54 (closed)