Use RGBDS 0.9.0 (#1159)

macros/code.asm

@@ -35,17 +35,11 @@ MACRO maskbits
 ; 	cp 26
 ; 	jr nc, .loop
 	assert 0 < (\1) && (\1) <= $100, "bitmask must be 8-bit"
-	DEF x = 1
-	rept 8
-		if x + 1 < (\1)
-			DEF x = (x << 1) | 1
-		endc
-	endr
+	DEF x = (1 << BITWIDTH((\1) - 1)) - 1
 	if _NARG == 2
-		and x << (\2)
-	else
-		and x
+		DEF x <<= \2
 	endc
+	and x
 ENDM
 
 MACRO calc_sine_wave