OpenGL2: Add run-time support for unsigned short indexes

OpenGL ES 2 is only required to support unsigned short for indexes.

code/renderergl2/tr_shade.c

@@ -40,7 +40,14 @@ R_DrawElements
 
 void R_DrawElements( int numIndexes, int firstIndex )
 {
-	qglDrawElements(GL_TRIANGLES, numIndexes, GL_INDEX_TYPE, BUFFER_OFFSET(firstIndex * sizeof(glIndex_t)));
+	if (tess.useCacheVao)
+	{
+		VaoCache_DrawElements(numIndexes, firstIndex);
+	}
+	else
+	{
+		qglDrawElements(GL_TRIANGLES, numIndexes, GL_INDEX_TYPE, BUFFER_OFFSET(firstIndex * sizeof(glIndex_t)));
+	}
 }
 
 
@@ -1720,6 +1727,8 @@ void RB_EndSurface( void ) {
 	tess.numIndexes = 0;
 	tess.numVertexes = 0;
 	tess.firstIndex = 0;
+	tess.useCacheVao = qfalse;
+	tess.useInternalVao = qfalse;
 
 	GLimp_LogComment( "----------\n" );
 }