We need different export decorators for the different libs.
For now no actual change though, just rename before the release,
and add prelude headers to define the new decorator to GST_EXPORT.
Simple implementation split from GstGLWindowWayland
Can now have multiple glimagesink elements all displaying output
linked via GL or otherwise (barring GL platform limitations).
The intel driver is racy and can crash setting up the two glimagesink contexts.
e.g.
videotestsrc ! tee name=t ! queue ! glupload ! glimagesinkelement
t. ! queue ! gleffects_blur ! glimagesinkelement
videotestsrc ! glupload ! glfiltercube ! tee name=t ! queue ! glimagesinkelement
t. ! queue ! gleffects_blur ! glimagesinkelement