Fix bug with page deletion. If inner page is removed and it tries to

Fix bug with page deletion. If inner page is removed and it tries to
remove page on next level linked from next inner page, ginScanToDelete()
wrongly sets parent page. Bug reveals when many item pointers from index
was deleted ( several hundred thousands).

Bug is discovered by hubert depesz lubaczewski <depesz@gmail.com>

Suppose, we need rc2 before release...