Get the BogoMIPS

Well, as I couldn't figure out why I didn't get interrupts from the PIT
after switched to the IOAPIC for interrupt handling, I just don't do it.

Interrupt setup is now split into two parts: setup_pic which remaps the
interrupts for the PIC of which IRQ 0 is then used by delay_init to get
the BogoMIPS value by means of the PIT and afterwards, the PIC is turned
off to use the IOAPIC later. Why not.

I believe the following error was present in the last commit, too, but has
nothing to do with the PIT problem: if it would have ever been called, the
pit_handler would have produced a divide error. That's fixed now and
everything works as expected. My qemu has a BogoMIPS of unbelievably low
265+/-10. My host had 6386.22 this boot. (And my measurement loop is even
much faster than Linux'.)

Just imagine me armed with a stop-watch sitting in front of the emulator
and measuring different time lapses while the sun is shining so lovely
outside :-)

OK, this obstacle finally out of the way, I hope to get SMP running today.
Don't clean the tools/

The occasional "make clean" always cleaned the tools/ until now. "Until now"
because it was annoying. It is a deepcl-only target now. I believe its
presence in the $(clean_targets) was a stupid error because tools/ was
listed in both cleaning target variables.
Drop early error handling

That's some code that doesn't really help much I think. If we can't access
the floppy or something, we're like screwed. Period.