Remove bias against partial pages in find_freeish_pages
The allocator fragments memory slightly less when it has freedom to
continue where it left off on a page.
Concerns of excessive conservativism no longer pertain.
Previously there could have been a ripple effect, if, say an object began at
the end of one page, consumed the next whole page, and two words more from the
page after that. A conservative reference from the stack would have pinned
thee pages worth of objects. This is no longer the case.