renderer: Make COGL_RENDERER / COGL_DRIVER env. variables case insensitive
renderer: Make COGL_RENDERER / COGL_DRIVER env. variables case insensitive

This will make it much more user friendly :-)

Reviewed-by: Neil Roberts <822ec91a7ef82248fd36162ca8ac3283eba70848@linux.intel.com>

collects/cogl,gcampax/cogl,Distrotech/cogl,djdeath/cogl,djdeath/cogl-android,Distrotech/cogl,gcampax/cogl,djdeath/cogl,gcampax/cogl,Distrotech/cogl,collects/cogl,djdeath/cogl-android,djdeath/cogl,gcampax/cogl,Distrotech/cogl,djdeath/cogl-android