Killed off vm86 code, no longer being used.

Implemented threading for x86_64.

* Thread creation and switching is working fine, however threads do not yet
get interrupted because I've not implemented hardware interrupt handling
yet (I'll do that next).
* I've made some changes to struct iframe: I've removed the e/r prefixes
from the member names for both 32/64, so now they're just named ip, ax,
bp, etc. This makes it easier to write code that works with both 32/64
without having to deal with different iframe member names.

Renamed remaining i386_* functions to x86_* for consistency.

Merged in the x86_64 exception handling.

I've split the 32-bit dependent IDT setup code and ASM interrupt handlers to
the 32 subdirectory, arch_int.cpp now contains only the generic hardware
interrupt handling code.

Killed off vm86 code, no longer being used.

Implemented threading for x86_64.

* Thread creation and switching is working fine, however threads do not yet
get interrupted because I've not implemented hardware interrupt handling
yet (I'll do that next).
* I've made some changes to struct iframe: I've removed the e/r prefixes
from the member names for both 32/64, so now they're just named ip, ax,
bp, etc. This makes it easier to write code that works with both 32/64
without having to deal with different iframe member names.

Renamed remaining i386_* functions to x86_* for consistency.

Merged in the x86_64 exception handling.

I've split the 32-bit dependent IDT setup code and ASM interrupt handlers to
the 32 subdirectory, arch_int.cpp now contains only the generic hardware
interrupt handling code.