While it's okay to use ';', the classic Merlin editor will treat it
as an end-of-line comment and shove the entire thing off to the right
side of the screen.
This adds a configuration item to the app settings, with a default
value of ';'.
Split into 6502/65816 portions. The 6502 version is the original
with a few in-place substitutions (e.g. JMP for BRL). The 65816
version is only needed to exercise special handling of PEA/PER.
