evas gl - fix compositing/native surface with egl/gles after glvnd

evas gl - fix compositing/native surface with egl/gles after glvnd

this fixes an issue that has cropped up in the past few months - only
nvidia drivers with egl/gles in x11... and compositing won't work
(native surface) and the introduction of libglvnd

it's a combination of libglvnd lying that it has symbols it can't
later find, new features to get core functions via procaddress that we
hadn't migrated to use AND use preferring core functions that libglvnd
will expose, so switching to KHR extensions by preference. we also
need to symmetrically use destroy image khr too...

oddly enough using procaddress purely for create/destroy image makes
wayland fail ... sofor now i'm taking advantage of the fact that
wayland has no extensions string passed in at the moment and still
doing dlsym... this is odd though.

@fix