trace: Fix alignment bug in computing image sizes.
trace: Fix alignment bug in computing image sizes.

Match precisely what the OpenGL spec says.

Fixes the stride computation of RGB8.

Based on discussion and code from Carl Worth and Paul Berry.

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