Missing functions to set some values in GSTEST and GSFRAME

[Fancy2209]

Currently, some stuff seems lacking from gsKit that I needed for a project:

• No function to set the FRAME FBMask (I tried setting this manually but it caused me issues, so I'm not sure how to properly do this mid frame, wanted to use it like how you'd use glColorMask)
• No function to set the Alpha Test's Method, Fail Method and Reference Value

I tried using these manually but I am not really sure what I am doing and messed up.