The @filename@ directive will use the full path of the file being parsed
for enumeration types; we should use @basename@, instead, as it improves
the reproducibility of the build by using only the file name.
glib-mkenums is not currently clever enough to know which version an
enum type was added in, so just mark all the _get_type() functions as
available in all versions.
This is part of a bunch of fixes for gcc complaining about
-Wmissing-declarations.
It puts functions into headers and includes those headers both where the
functions are defined and where they function are used.
