The param option just contains an options object, not a separate
capabilities. Also even when passing the options object across the wire,
the capabilities within this object are not part of the "options". These
are actually handled separated by GimpExportProcedure.
Therefore the changes are:
* GimpExportCapabilities moved to gimpbaseenums.h with a proper GType.
* "capabilities" properties are changed to flags param spec with type
GimpExportCapabilities.
* GimpParamSpecExportOptions doesn't have a capabilities variable
anymore.
* Consequently gimp_param_spec_export_options() doesn't have a
capabilities arg.
* Wire protocol updated as we don't need to pass any capabilities
neither for the param definition, nor for the argument values.
* GimpExportOptionsEditFunc renamed GimpExportGetCapabilitiesFunc and
returning GimpExportCapabilities flags, instead of setting the
"capabilities" property. I believe it makes it much more obvious what
this callback is for and how to use it.
* Annotations improved or completed.
* Don't make the GimpParamSpecExportOptions public anymore since it is
the same as its parent.
a0fa9cc191