m4macros: add GLIB_CONFIG, deprecate AM_PATH_GLIB_2_0

Add a new GLIB_CONFIG macro, which is mostly similar to the old
AM_PATH_GLIB_2_0, but correctly namespaced, and with parts of
GLIB_GSETTINGS added, and support for GLIB_VERSION_MIN_REQUIRED and
GLIB_VERSION_MAX_ALLOWED.
2 files changed