Make all GDK_DEPRECATED and GDK_AVAILABLE macros use a
new _GDK_EXTERN macro. _GDK_EXTERN defaults to just 'extern'
but a subsequent commit will add visibility handling to it
while building GTK+.
Add a macro to declare that a particular symbol is available in all
versions of GTK+.
All newly-added symbols should have proper version macros (like
GDK_AVAILABLE_IN_3_4).
.. instead of the previous stable version.
This ensures that if we use GDK_DEPRECATED_IN_3_6, it will actually emit
a warning in GTK 3.5, and not wait with that until GTK 3.7. This is
particularly useful for stuff that gets deprecated right now. This code
should emit warnings right now, so we know what we're doing while
deprecating.
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.
