5.0-2712 made ES's code for setting the game ID use the
title ID converted to hex (except for disc titles) instead
of using a 6-char game ID like before. Then, 5.0-2830 made
us use that code even when loading game INIs. This breaks the
expectations of both users and the game INIs we ship with.
This commit makes Dolphin use 6-char game IDs for all
titles (unless the 6-char ID would contain unprintable
characters, which is the case with e.g. the Wii Menu).
I'm also putting unprintability checks in VolumeWad
for consistency.