gl: g-i: expose platform-specific display API in bindings

https://bugzilla.gnome.org/show_bug.cgi?id=786391

gst-libs/gst/gl/Makefile.am

@@ -87,6 +87,9 @@ libgstgl_@GST_API_VERSION@_la_LIBADD = \
 	$(GST_LIBS) \
 	$(GL_LIBS)
 
+gstgl_gir_headers = $(libgstgl_@GST_API_VERSION@include_HEADERS)
+gstgl_gir_sources = $(libgstgl_@GST_API_VERSION@_la_SOURCES)
+
 if HAVE_WINDOW_WIN32
 SUBDIRS += win32
 libgstgl_@GST_API_VERSION@_la_LIBADD += win32/libgstgl-win32.la
@@ -100,11 +103,15 @@ endif
 if HAVE_WINDOW_X11
 SUBDIRS += x11
 libgstgl_@GST_API_VERSION@_la_LIBADD += x11/libgstgl-x11.la
+gstgl_gir_headers += x11/gstgldisplay_x11.h
+gstgl_gir_sources += x11/gstgldisplay_x11.c
 endif
 
 if HAVE_WINDOW_WAYLAND
 SUBDIRS += wayland
 libgstgl_@GST_API_VERSION@_la_LIBADD += wayland/libgstgl-wayland.la
+gstgl_gir_headers += wayland/gstgldisplay_wayland.h
+gstgl_gir_sources += wayland/gstgldisplay_wayland.c
 endif
 
 if HAVE_WINDOW_DISPMANX
@@ -130,6 +137,8 @@ endif
 if USE_EGL
 SUBDIRS += egl
 libgstgl_@GST_API_VERSION@_la_LIBADD += egl/libgstgl-egl.la
+gstgl_gir_headers += egl/gstgldisplay_egl.h
+gstgl_gir_sources += egl/gstgldisplay_egl.c
 endif
 
 configexecincludedir = $(libdir)/gstreamer-@GST_API_VERSION@/include/gst/gl
@@ -153,8 +162,8 @@ DISTCLEANFILES = $(built_sys_header_configure)
 if HAVE_INTROSPECTION
 BUILT_GIRSOURCES = GstGL-@GST_API_VERSION@.gir
 
-gir_headers=$(patsubst %,$(srcdir)/%, $(libgstgl_@GST_API_VERSION@include_HEADERS))
-gir_sources=$(patsubst %,$(srcdir)/%, $(libgstgl_@GST_API_VERSION@_la_SOURCES))
+gir_headers=$(patsubst %,$(srcdir)/%, $(gstgl_gir_headers))
+gir_sources=$(patsubst %,$(srcdir)/%, $(gstgl_gir_sources))
 
 GstGL-@GST_API_VERSION@.gir: $(INTROSPECTION_SCANNER) libgstgl-@GST_API_VERSION@.la
 	$(AM_V_GEN)PKG_CONFIG_PATH="$(GST_PKG_CONFIG_PATH)" GI_SCANNER_DISABLE_CACHE=yes\