Export GES library API in headers when we're building the
library itself, otherwise import the API from the headers.
This fixes linker warnings on Windows when building with MSVC.
Fix up some missing config.h includes when building the lib which
is needed to get the export api define from config.h
Fixes https://gitlab.freedesktop.org/gstreamer/gst-editing-services/issues/42
g-ir-scanner includes section docs as class/interface docs if the section name is equal to the lowercase type name.
Since all the documentation is in section blocks, rename them to match the type names.
https://bugzilla.gnome.org/show_bug.cgi?id=727776
The priority handling of clip is now handled by GESLayer itself, and
handling clip as a ordered list should be implemented in GESLayer itself
too, this way the user can decide to switch mode at any time instead of
