Add Lua migration helper library for bitwise ops

see 49cd836e1, #3485
put `bit = (require "migration_helpers").EmuHawk_pre_2_9_bit();` at top of file
can now easily add helpers for migrating from other emulators

Assets/Lua/migration_helpers.lua

@@ -0,0 +1,22 @@
+local helpers = {};
+helpers.EmuHawk_pre_2_9_bit = function()
+	local wrapped_bit = {
+		band = function(val, amt) return val & amt; end,
+		bnot = function(val) return ~val; end,
+		bor = function(val, amt) return val | amt; end,
+		bxor = function(val, amt) return val ~ amt; end, -- not a typo
+		lshift = function(val, amt) return val << amt; end,
+		rol = bit.rol,
+		ror = bit.ror,
+		rshift = function(val, amt) return val >> amt; end,
+		arshift = bit.arshift,
+		check = bit.check,
+		set = bit.set,
+		clear = bit.clear,
+		byteswap_16 = bit.byteswap_16,
+		byteswap_32 = bit.byteswap_32,
+		byteswap_64 = bit.byteswap_64,
+	};
+	return wrapped_bit;
+end;
+return helpers;