Removed unused vertex/triangle optimization code

When enabled, the renderer won't compile.
When this is fixed, map load times are increased dramatically without any improvement to runtime performance and very little difference to vertex/index counts.
Remove unused shader "models/buildables/drill/energy".
Add back a commented version of "models/buildables/drill/energy" since it's used by the low poly drill model.
Cleanup a cast inside generic_vp.glsl.
Error out if an extra pak can not be found
Make modelist print to regular log not developer. Remove extra newlines
Remove unused variable
When the areaportalMask changes invalidate all cached clusters.

Invalidating only the current view cluster is not enough, because the
player can walk back into an already cached cluster which then would
be drawn based on the old areamask setting.
Merge branch 'master' into for-0.26