Lots of improvements, including restructring the caching and management

Lots of improvements, including restructring the caching and management
of vnodes and objects.  There are some metadata performance improvements
that come along with this.  There are also a few prototypes added when
the need is noticed.  Changes include:

1) Cleaning up vref, vget.
2) Removal of the object cache.
3) Nuke vnode_pager_uncache and friends, because they aren't needed anymore.
4) Correct some missing LK_RETRY's in vn_lock.
5) Correct the page range in the code for msync.

Be gentle, and please give me feedback asap.