MFC r289895:
Reduce the amount of calls to VOP_BMAP() made from the local vnode
pager.

MFC r291157, r291158:
Include the pages before/after the requested page, that fit into the
reqblock, into the calculation of the size of run of pages.

Tested by: pho

MFC 261811,282660,282706:
Place VM objects on the object list when created and never remove them.

261811:
Fix function name in KASSERT().

282660:
Place VM objects on the object list when created and never remove them.
This is ok since objects come from a NOFREE zone and allows objects to
be locked while traversing the object list without triggering a LOR.

Ensure that objects on the list are marked DEAD while free or stillborn,
and that they have a refcount of zero. This required updating most of
the pagers to explicitly mark an object as dead when deallocating it.
(Only the vnode pager did this previously.)

282706:
Satisfy vm_object uma zone destructor requirements after r282660 when
vnode object creation raced.

MFC r271586:
Fix mis-spelling of bits and types names in the vnode_pager_putpages().

Approved by: re (delphij)

MFC 261811,282660,282706:
Place VM objects on the object list when created and never remove them.

261811:
Fix function name in KASSERT().

282660:
Place VM objects on the object list when created and never remove them.
This is ok since objects come from a NOFREE zone and allows objects to
be locked while traversing the object list without triggering a LOR.

Ensure that objects on the list are marked DEAD while free or stillborn,
and that they have a refcount of zero. This required updating most of
the pagers to explicitly mark an object as dead when deallocating it.
(Only the vnode pager did this previously.)

282706:
Satisfy vm_object uma zone destructor requirements after r282660 when
vnode object creation raced.

MFC r271586:
Fix mis-spelling of bits and types names in the vnode_pager_putpages().

Approved by: re (delphij)