configure.ac: ignore COGL_PANGO_DEPS if cogl-pango disabled
configure.ac: ignore COGL_PANGO_DEPS if cogl-pango disabled

This skips the pkg-config check for COGL_PANGO_DEPS if
--disable-cogl-pango was explicitly passed to ./configure.

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

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