page->flags cleanup.

Moves the definitions of the page->flags bits and all the PageFoo
macros into linux/page-flags.h.  That file is currently included from
mm.h, but the stage is set to remove that and include page-flags.h
direct in all .c files which require that.  (120 of them).

The patch also makes all the page flag macros and functions consistent:

For PG_foo, the following functions are defined:

	SetPageFoo
	ClearPageFoo
	TestSetPageFoo
	TestClearPageFoo
	PageFoo

and that's it.

- Page_Uptodate is renamed to PageUptodate

- LockPage is removed.  All users updated to use SetPageLocked

- UnlockPage is removed.  All callers updated to use unlock_page().
  it's a real function - there's no need to hide that fact.

- PageTestandClearReferenced renamed to TestClearPageReferenced

- PageSetSlab renamed to SetPageSlab

- __SetPageReserved is removed.  It's an infinitesimally small
   microoptimisation, and is inconsistent.

- TryLockPage is renamed to TestSetPageLocked

- PageSwapCache() is renamed to page_swap_cache(), so it doesn't
  pretend to be a page->flags bit test.