(0/4) stack updates for x86

The kernel currently uses an 8k stack, per task. Here is the infrastructure needed to allow us to halve that. The original work was by Ben LaHaise. I broke it out into several patches and updated it for the current kernels.

A-thread_info_cleanup-2.5.50+bk-5.patch
Gets asm-i386/thread_info.h ready for the irqstack and overflow detection patches

B-interrupt_stacks-2.5.50+bk-5.patch
Have special stacks for use in interrupts.

C-stack_usage_check-2.5.50+bk-5.patch
Check for stack overflows on entry to each funtion. Use gcc's -p profiling feature to do it.

D-4k-stack-2.5.50+bk-5.patch
make a config option to turn on 4k stacks. (there appears to be a problem with this right now).

Dave Hansen
[email protected]