Correct spelling mistakes.

code/renderergl2/tr_backend.c

@@ -471,7 +471,7 @@ void RB_RenderDrawSurfList( drawSurf_t *drawSurfs, int numDrawSurfs ) {
 
 		//
 		// change the tess parameters if needed
-		// a "entityMergable" shader is a shader that can have surfaces from seperate
+		// a "entityMergable" shader is a shader that can have surfaces from separate
 		// entities merged into a single batch, like smoke and blood puff sprites
 		if ( shader != NULL && ( shader != oldShader || fogNum != oldFogNum || dlighted != oldDlighted || pshadowed != oldPshadowed || cubemapIndex != oldCubemapIndex
 			|| ( entityNum != oldEntityNum && !shader->entityMergable ) ) ) {
@@ -689,7 +689,7 @@ void RE_StretchRaw (int x, int y, int w, int h, int cols, int rows, const byte *
 		RB_EndSurface();
 	}
 
-	// we definately want to sync every frame for the cinematics
+	// we definitely want to sync every frame for the cinematics
 	qglFinish();
 
 	start = 0;