#147 OnBA: Caching of .inc files

[Steve Little]

Would be good to cache .inc files, so that they don't
have to be reparsed all the time. For example the
systraps.inc file takes quite a while to parse each time,
probably more than a small asm program in fact...

Like with OnBC, we could offer a 'purge .inc cache'
option to force rebuilding if and when they change.

And/or a menu option to switch off caching for those
who don't want it.