cogl-vertex-attribute: Fix the name of the cogl_normal_in attribute
cogl-vertex-attribute: Fix the name of the cogl_normal_in attribute

The builtin vertex attribute for the normals was incorrectly checked
for as 'cogl_normal' however it is defined as cogl_normal_in in the
shader boilerplate and for the name generated by CoglVertexBuffer.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2499

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