AVALANCHE: Partially implement Help::getMe().

The drawing of the buttons are still missing.
AVALANCHE: Move/rename/implement Help::plotButton().
PEGASUS: Fix returning from Mars after destroying the robot's shuttle
SDL: Add debugging code to output SDL audio driver name being used.

This is to aid with investigation of bug #6510 - "SDL: Audio delay in
daily builds" and similar future issues.
SDL: Add debugging code to output SDL video driver name being used.
OPENGL: Properly use signed types for cursor hotspot.
OPENGL: Use signed types for mouse coordinates.

This adjusts for the fact that our event handling also uses signed coordinates.
OPENGL: Use GLfloat for draw cooridnates in Texture.
OPENGL: Simplify shake offset application.
OPENGL: Use frac_t for cursor scaling.
OPENGL: Move RGBA8888 (logical layout) to OpenGL specific formats.

The reason here is that GL_UNSIGNED_INT_8_8_8_8 is not supported by the GLES
standard. Thus we cannot use it outside OpenGL specific code paths.
OPENGL: Always support RGBA8888 (memory layout).
OPENGL/SDL: Default to RGBA8888 (memory layout).

This makes sure the default mode also works for OpenGL ES contexts.
WINTERMUTE: Use game format for fallback font rendering.

BDF fonts got 32bit drawing support in ece8b7fb65402238ab7df896361a9cefe28b8897
Thus it is not necessary to draw onto a 16bit surface.