Add test for multiple vertex sources
Add test for multiple vertex sources

acolley/glium,glium/glium,caldwell/glium,carbidegames/glium,sdotz/glium,christopheraugustus/glium,msiglreith/glium,nicokoch/glium,binsoftware/glium,cpjreynolds/glium,TyOverby/glium,tomaka/glium,rozaliev/glium,bvssvni/glium