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.
Except for gst/gl/gstglfuncs.h
It is up to the client app to include these headers.
It is coherent with the fact that gstreamer-gl.pc does not
require any egl.pc/gles.pc. I.e. it is the responsability
of the app to search these headers within its build setup.
For example gstreamer-vaapi includes explicitly EGL/egl.h
and search for it in its configure.ac.
For example with this patch, if an app includes the headers
gst/gl/egl/gstglcontext_egl.h
gst/gl/egl/gstgldisplay_egl.h
gst/gl/egl/gstglmemoryegl.h
it will *no longer* automatically include EGL/egl.h and GLES2/gl2.h.
Which is good because the app might want to use the gstgl api only
without the need to bother about gl headers.
Also added a test: cd tests/check && make libs/gstglheaders.check
https://bugzilla.gnome.org/show_bug.cgi?id=784779
e.g when wrapping a data pointer we don't want to map/unmap off the end of
pointer with the alignment bytes.
Instead track that information separately as maxsize is used for mapping by
GstMemory and thus represents a size without any alignment padding bytes.
This is made possible by a subclassable GstGLAllocationParams that holds
the allocation parameters
Every allocation would now go through gst_gl_base_memory_alloc with the
allocation parameters now being specified in a single struct to allow
extension by different allocators.
It handles the following
- GstAllocationParams -> gst_memory_init transformation
- Makes sure that map/unmap/create/destroy happen on the GL thread with
a GL context current.
- Holds a possible sysmem accessible data pointer with alignment.
- Holds the need upload/download transfer state
