Convert all the bulk callers of lru_cache_del() to use the batched
pagevec_lru_del() function.

Change truncate_complete_page() to not delete the page from the LRU.
Do it in page_cache_release() instead.  (This reintroduces the problem
with final-release-from-interrupt.  THat gets fixed further on).

This patch changes the truncate locking somewhat.  The removal from the
LRU now happens _after_ the page has been removed from the
address_space and has been unlocked.  So there is now a window where
the shrink_cache code can discover the to-be-freed page via the LRU
list.  But that's OK - the page is clean, its buffers (if any) are
clean.  It's not attached to any mapping.