- Fix build on ARM:

- Fix build on ARM:
  - _iob is already defined as a dll_import
  - _rotl intrinsic is now implemented (should use rol instruction, but not sure on the syntax!)
  - Add a stub psctx.h for ARM
  - Added InterlockedEXchangePointers
  - Fix uninitialized variable warning in ex/resource.c
- Start to implement interrupt handling:
  - We now have a rudimentary interrupt handler that takes care of software interrupts
  - We now have a rudimentary DPC handler which takes care of switching to the next thread, if any
  - We now setup the HAL Interrupt Source -> IRQL Table (The IRQLMask Table).
  - Implemented HalGetInterruptSource, which allows us to get the interrupt # that cause the IRQ.
    Note: this wasn't needed on Alpha/PPC/MIPS NT ports, because that information is stored on the CPU,
    and the kernel could read it -- we must abstract it through the HAL.
  - Add the OldIrql to the TRAP_FRAME, we don't use it yet.
- We are now ready to context switch to the Phase 1 thread.

svn path=/trunk/; revision=33933