Currently the page fault handler on the x86 can get a clobbered value
for %cr2 if an interrupt occurs and causes another page fault (interrupt
handler touches a vmalloced area for example) before %cr2 is read.  This
patch changes the page fault and alignment check (currently unused)
handlers to interrupt gates so that %cr2 can be read before an interrupt
can occur.  I'm not certain how much of a problem this really is, but I
suspect it could cause random seg faults to user space under heavy
interrupt load.  Comments are welcome.