[This has four scalps already.  Thomas Molina has agreed
 to track things as they are identified ]

Infrastructure to detect sleep-inside-spinlock bugs.  Really only
useful if compiled with CONFIG_PREEMPT=y.  It prints out a whiny
message and a stack backtrace if someone calls a function which might
sleep from within an atomic region.

This patch generates a storm of output at boot, due to
drivers/ide/ide-probe.c:init_irq() calling lots of things which it
shouldn't under ide_lock.

It'll find other bugs too.