This patch (made against linux-2.4.4-pre2) takes Anton Blanchard's suggestions
and abstracts out the rwsem implementation somewhat. This makes the following
general files:

	include/linux/rwsem.h		- general RW semaphore wrapper
	include/linux/rwsem-spinlock.h	- rwsem inlines implemented in C
	include/asm-xxx/rwsem.h		- arch specific rwsem details
	lib/rwsem.c			- contention handlers for rwsems

The asm/rwsem.h file is responsible for specifying whether the general
default implementation should be used, or supplying an alternative optimised
implementation if not.

For the i386 arch, I've supplied the following:

	include/asm-i386/rwsem.h	- i386 specific rwsem details
	include/asm-i386/rwsem-xadd.h	- i386 XADD optimised rwsems
	include/asm-i386/rwsem-spin.h	- i386 optimised spinlocked rwsems
	arch/i386/lib/rwsem.S		- i386 call wrapper stubs

I haven't changed any of the other arch's, but until their semaphore.h's refer
to linux/rwsem.h, they'll continue to use whatever method they currently
happen to use. Note that the contention handling functions have been renamed
to prevent name clashes with the old contention functions.

David