Fix cogl_texture_get_data when an intermediate buffer is used
Fix cogl_texture_get_data when an intermediate buffer is used

When an intermediate buffer is used for downloading texture data it
was using the wrong byte length for a row so the copy back to the
user's buffer would fail.

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