fix .xbox360 support

[udance4ever]

Hi! Back in RetroBat land (see you've made a lot of progress!)

I just got all my xbox360 games up and running in RetroBat (yeay!)

The format for an XBLA Ilomilo.m3u is:

\Ilomilo\58410A1B\000D0000\D2BAC6E5571A96D5BB3CEF0F1A3F4F25709C951358<no CR>

I discovered that .m3u can be used as a stub file for GoD (Game on Disc) folders (Final Fantasy XIII (USA-EU).m3u):

\Final Fantasy XIII (USA-EU)\default.xex<no CR>

equivalent .xbox360 files

Ilomilo.xbox360

Ilomilo/58410A1B/000D0000/D2BAC6E5571A96D5BB3CEF0F1A3F4F25709C951358<CR optional>

Final Fantasy XIII (USA-EU).xbox360

./Final Fantasy XIII (USA-EU)/default.xex<CR optional>

Currently these two .xbox360 files do not boot. The workaround, of course, is to use a script to change the formatting.

I think the way to address this issue is to use the same grammar to process .m3u and .xbox360 with the following rules:

1. treat forward (/) and backslashes (\) as equivalent
2. make the leading slash (\) optional (leaving it out is technically more correct as a relative path)
3. make the trailing CR (carriage return) optional (CR must be left out for .m3u and it would be ideal to handle both cases as many editors often add a "missing" newline at the end of a file)

It would be preferable to use existing .xbox360 working in Batocera Linux in RetroBat for maximum cross-platform compatibility as the Xbox360 rom collection can get quite large.

Support was first implemented in #174