vastspace: Delete unused source file
Fix ShadowMap::getAdditive() returned corrupted pointer

The OpenGLState::weak_ptr tend to make a mess.  We need to watch it to
prevent runtime errors.
Mesh: Supported multiple textures when drawing with VBO

We have done this in sufvbo.c but have not properly ported to
Mesh::draw().
Prevent MTurret::draw() from crashing the process

It should quit using obsolete precompiled .bin files and switch to
.mqo files, but in the meantime, we just make it not break everything.
vastspace: Move SpacePlane model to mods subdirectory
vastspace: Add additional texture images for SpacePlane

The images are originally for Destroyer's and we just borrowed it
for engine texture, but the module should have its own copy because
that invisible dependency will mess up things.
vastspace: Separated SpacePlane-draw.cpp from SpacePlane.cpp

Also switched model source from obsolete compiled .bin files to the
original .mqo files.