improved Wii support (including "split cores")

[markwkidd]

Bounty contributions make a difference - please donate at this link today to support this enhancement

Wiimpathy from gbatemp was gracious enough to send this diff patch which has some clues about two things regarding Wii (not WiiU):

1. #ifdefs in the general codebase that improve the experience for Wii users
2. Makefile changes to produce the "split cores" that are necessary for mame2003-plus to fit in the memory constraints of the original Wii

We could try to implement these. For now I wanted to make an issue so it could be tracked:

Mame2003-plus_Wii_0.zip

The discussion and the full source is here: https://gbatemp.net/threads/mame-2003-plus.499497/

[mahoneyt944]

Handling this issue in #1416