Almost fix function overloading. Return var issues.

test/constant_buffer.shd

@@ -4,7 +4,9 @@ camera :: constant_buffer {
 }
 
 vertex main :: (pos : float4 @position) -> float4 @position {
-	return mul(camera.projection, mul(camera.view, pos));
+	mv : float4 = mul(camera.view, pos);
+	mvp : float4 = mul(camera.projection, mv);
+	return mvp;
 }
 
 pixel main :: () -> float4 @target {