[049/906] * configure.ac: * sys/glsink/glextensions.c: * sys/glsink/glextensions...

[049/906] * configure.ac: * sys/glsink/glextensions.c: * sys/glsink/glextensions.h: * sys/glsink/glimagesink.c: * sys/glsink/glimagesink.h: * sys/glsink/gstglbuffer.c: * sys/glsink/gstglbuffer.h: * sys/glsink/gstglconvert.c: * sys/glsink/gstgldisplay.c: * sys/glsink/gstgldisplay.h: * sys/glsink/gstgldownload.c: * sys/glsink/gstglfilter.c: * sys/glsink/gstglfilter.h: * sys/glsink/gstglfilterexample.c: * sys/glsink/gstgltestsrc.c: * sys/glsink/gstglupload.c: Major cleanup of code.  Convert glupload to BaseTransform. Handle caps negotiation mostly correctly.  Reenable in build.