loading float constants for GLSL.

- DrawPrim is just too big of a function.  This separates the passing
  of constants to the shader into new functions.
- Fixes an off-by-one error when loading vertex declaration constants
  (should be <, not <=)
- Adds a function for GLSL loading of constants (aka Uniforms)
- Adds a GLSL program variable to the stateblock and sets it to 0 (a
  future patch will actually create this program)