#20 OGL_Blitter enhancements

[Jeremiah Morris]

This patch makes the projection-setting part of OGL_Blitter optional, so that it can be used in already set-up projections. It also accepts source and destination rectangles at Draw time, like the HUD DrawShape routines.

The HUD renderer now uses OGL_Blitter instead of its own similar code, and the terminal and loading-screen uses were cleaned up a bit, to use real screen coordinates where practical.

[Jeremiah Morris]