These macros follow the recent changes in GLibs deprecation
setup. We now annotate deprecated functions with the version
they were deprecated in, and you can define the macro
GDK_VERSION_MIN_REQUIRED to cut off deprecation warnings for
'recent' deprecations.
At the same time, we introduce version annotations for new API
and allow you to avoid 'recent' API additions by defining
GDK_VERSION_MAX_ALLOWED.
