Don't map vertex buffer object data in memory.

Stop depending on glMapBufferARB, use glBufferSubDataARB to be more
OpenGL ES friendly.
Use single variable for texture bit depth.

Replace ‘gl_texture(alpha|solid)mode’ variables with ‘gl_texturebits’.
Use GL_RGB for solid textures by default, as it appears to be slightly
faster.
Update existing draw object if already created.
Reset screen scaling after drawing loading plaque.