We should refactor the texture creation code so that it can be reused in a number
of situations. The current code base has a couple problems:
  - the texture object creation code is duplicated for both the shared
    initTexture() method and for the initPbuffer() method (on Windows only)
  - the initTexture() method always creates an GL_RGBA texture even if the
    alpha channel will never be used (potential waste of VRAM)
  - the initPbuffer() method (on Windows) doesn't check for the texNonPow2
    extension (if it did, and the extension was available, then we could
    potentially save VRAM)

Also, there are some upcoming changes that would be much easier if we refactored
this code:
  - to support the GL_EXT_framebuffer_object extension, it would be
    nice if we could just delegate to this one shared method for creating the
    texture object
  - to support translucent VolatileImages, we need a way to create an RGBA
    texture, so having an isOpaque boolean parameter for the shared texture
    creation method would make things easier

###@###.### 2005-05-29 20:07:36 GMT