Make it possible for applications to have the kernel free memory
lazily.  This reduces a repeated free/malloc cycle from freeing
pages and allocating them, to just marking them freeable.  If the
application wants to reuse them before the kernel needs the memory,
not even a page fault will happen.

This version has one bugfix over the last one: if a PG_lazyfree
page was found dirty at fork time, we clear the flag in
copy_one_pte().

Ulrich Drepper has test glibc RPMS for this functionality at:

	http://people.redhat.com/drepper/rpms

Because MADV_FREE has not been defined as a fixed number yet,
for the moment MADV_DONTNEED is defined to have the same
functionality.

Any test results of this patch in combination with Ulrich's
test glibc are welcome.

-- 
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.