* configure.ac: * sys/glsink/Makefile.am: Switch to using pkgconfig to detect libGL.  Since we use recent features added to Mesa, there's no point in adding a check for pre-pkgconfig versions.
* configure.ac:
* sys/glsink/Makefile.am:
Switch to using pkgconfig to detect libGL.  Since we use
recent features added to Mesa, there's no point in adding
a check for pre-pkgconfig versions.

mapmapteam/gst-plugins-gl,ystreet/gst-plugins-gl,mapmapteam/gst-plugins-gl,mapmapteam/gst-plugins-gl,ystreet/gst-plugins-gl,ystreet/gst-plugins-gl