package/libglib2: bump to version 2.68.1

Other changes:
  - Drop 0002-allow-explicit-disabling-of-tests.patch as this patch has been
    upstreamed and the option is now simply "tests."
  - Add -Dglib_debug=disabled and -Dlibelf=disabled as defaults to both
    HOST_LIBGLIB2_CONF_OPTS and LIBGLIB2_CONF_OPTS
  - Refactor existing patches to apply to 2.68.1

Tested with test-pkg -p libglib2 -a.

Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>