System call restart support.

Implemented the rest of the kernel debugger functions for x86_64.

Merged with the x86 implementations, mostly the same except for a
few differences. GDB stub is currently broken, will investigate
later.

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.

Merged x86_64 headers into x86 headers.

Not many changes seeing as there's not much x86_64 stuff done yet. Small
differences are handled with ifdefs, large differences (descriptors.h,
struct iframe) have separate headers under arch/x86/32 and arch/x86/64.

System call restart support.

Implemented the rest of the kernel debugger functions for x86_64.

Merged with the x86 implementations, mostly the same except for a
few differences. GDB stub is currently broken, will investigate
later.

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.

Merged x86_64 headers into x86 headers.

Not many changes seeing as there's not much x86_64 stuff done yet. Small
differences are handled with ifdefs, large differences (descriptors.h,
struct iframe) have separate headers under arch/x86/32 and arch/x86/64.