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.
Merge pull request #8 from marioaugustorama/master

Fix formatting.
README.md: quick follow up fix
msx2: Make the cursor work

I was clearly not awake pasting the initial cursor code together.

This gives us a correct text rendering, except for the mysterious double
copy which presumably is a VDP set up error of some kind.
msx2: various platform side and vdp fixes

With these and the small core fixes to follow we blow up for reasons I don't
yet understand in the uput() call in create_init. Presumably some kind of
mapping setup bug. With that commented we hit the boot device request, at
which point we have no keyboard.

Display is still wonky. Guess it wants an MSXpert to figure out whats wrong
with the 80x25 setup
lowlevel-z80: various (important) fixes

1.	Exit with reti, most platforms don't care but a few do so avoid
	digging holes

2.	MSX2 is the first platform we handle where not servicing an IRQ
	jams you in a loop. Provide a hook to always service some interrupts
	even if we are on an IRQ stack or otherwise detained from calling
	platform_interrupt

3.	The di() call saved the flags but forgot to DI, this fixes several
	rather odd bugs I'm sure

4.	The signal processing on irq return is suspect, note it for future
	sorting out.

With this and the MSX2 fixes we get closer to a basic MSX2 boot
platforms: add platform_interrupt_all everywhere