cpu: introduce "staticfast"

On Z80 and to an extent 6502 we gain a lot if we can pin some of our
auto variables to static addresses. Clearly this can only be done for
non-re-entrant functions but our architecture means we have plenty of them

6809 is not really so aflicted so uses auto.
filesys/syscall2: optimise a few spots with staticfast
syscall_other: optimisations

Cache the inode calculation in execve, otherwise each loop pass must recompute
it as the compiler can't know the functions don't touch it.

Add a couple of staticfasts
msx2: further work on video - closer

We now get the font, and most of the text. The move to a new line keeps
wiping the start of the next, and it appears twice.