Fixed screen brightness problems (tested on 1.0.0 and 2.0.0). Some refactoring.

ipl/btn.c

@@ -37,22 +37,21 @@ u32 btn_wait()
 	u32 res = 0, btn = btn_read();
 	int pwr = 0;
 
-	// Power button down, raise a filter.
+	//Power button down, raise a filter.
 	if (btn & BTN_POWER)
 	{
 		pwr = 1;
-		btn &= 0xFFFFFFFE;
+		btn &= ~BTN_POWER;
 	}
 
 	do
 	{
 		res = btn_read();
-		// Power button up, remove filter.
+		//Power button up, remove filter.
 		if (!(res & BTN_POWER) && pwr)
 			pwr = 0;
-		// Power button still down.
-		else if (pwr)
-			res &= 0xFFFFFFFE;
+		else if (pwr) //Power button still down.
+			res &= ~BTN_POWER;
 	} while (btn == res);
 
 	return res;