glstate: Use GL_RGB whenever possible.
glstate: Use GL_RGB whenever possible.

Now that 3-channel floating point PNMs are fixed, using GL_RGB
saves memory/time.

schulmar/apitrace,swq0553/apitrace,surround-io/apitrace,joshua5201/apitrace,joshua5201/apitrace,swq0553/apitrace,swq0553/apitrace,tuanthng/apitrace,apitrace/apitrace,apitrace/apitrace,tuanthng/apitrace,trtt/apitrace,surround-io/apitrace,trtt/apitrace,trtt/apitrace,schulmar/apitrace,EoD/apitrace,tuanthng/apitrace,schulmar/apitrace,tuanthng/apitrace,EoD/apitrace,schulmar/apitrace,swq0553/apitrace,surround-io/apitrace,surround-io/apitrace,trtt/apitrace,trtt/apitrace,EoD/apitrace,joshua5201/apitrace,joshua5201/apitrace,tuanthng/apitrace,schulmar/apitrace,apitrace/apitrace,EoD/apitrace,EoD/apitrace,apitrace/apitrace,surround-io/apitrace,joshua5201/apitrace,swq0553/apitrace