consistently name cogl-gles2 pkg-config files

This makes sure we install a cogl-gles2-1.0.pc and
cogl-gles2-2.0-experimental.pc file consistent with other sub-libraries
such that cogl-1.x packages can be parallel installed with cogl master.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
Consistently name cogl-gst pkg-config files

This makes sure we install a cogl-gst-1.0.pc and
cogl-gst-2.0-experimental.pc file consistent with other sub-libraries
such that cogl-1.x packages can be parallel installed with cogl master.

Reviewed-by: Neil Roberts <neil@linux.intel.com>