Update alpha handling to clip (alpha*255) to 0-255  

Drawing events inside ENIGMA already had its (alpha*255) clipped to 0-255, I simply expanded this to the DX9, GL1, and GL3 rendering.   Clips (alpha*255) to 0-255.   User alpha values > 1 will be 1 and < 0 will be 0.  This will also help prevent any 1 frame glitches when using certain fractional incremental/decremental in alpha values (for example when using fade in / fade out effects).  With this in place, we now are handling things like GMS and other game development tools.  Some might argue that you could do this yourself using IF, however when using certain high precision fractional ranges as you get closer to the target range some unexpected jump in value might occur causing a glitch.  

Tested in DX9, OpenGL1, OpenGL3.