+ implement true memory barriers for all architectures

+ implement true memory management
  + [ia32] use int 0x15 ax=0xe820 to get memory map and memory size	[DONE]
  + [mips] use some heuristics to get memory map and memory size
  + reimplement heap so that it can allocate/deallocate
    itself frames as necessary
  + provide native four-level portable page table interface		[DONE]
    + every architecture uses its native page table format
    + kernel provides unified four-level page table interface
      for all architectures
  + track usage of frames containing middle-level page tables
    (frame leak)

+ get user mode support for all architectures

+ save/restore floating point context on context switch 
  + [ia32] lazy context switch using TS flag                            [DONE]
+ [ia32] MMX,SSE1-.. initialization
+ [ia32] review privilege separation                                    [DONE]
  + zero IOPL in EFLAGS                                                 [DONE]
  + before IRET (from SYSCALL), zero NT in EFLAGS                       [DONE]
+ [ia32] review the cache controling bits in CR0 register
+ [ia32] zero the alignment exception bit in EFLAGS                     [DONE]
  - Task changed to clear AM in CR0 so that
    the alignment check is disabled globally
+ make emulated architectures also work on real hardware