Remove (un)committed pages distinction

Remove (un)committed pages distinction

This distinction is only made by Windows, and adds an extra complexity
that probably doesn't worth it (specially for other OSs, where this adds
a little overhead too, in both space and time).

Other OSs (like Linux) even do all the committing automatically, under the
hood, see:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;\
f=Documentation/vm/overcommit-accounting;hb=HEAD