Revert "fixes #327"
Revert "fixes #327"

This reverts commit a80ec2e259a60ff094a62b43032efe6a5584dd9e.

This papered over the issue of NaNs being in the index's
last_rows causing search_last_row to always be incorrect.

This can be tested by a testcase that searches for x > 0 where x values
are:

1 1 1 1 ... 1 NaN 1 NaN 1
[ chunks    ] [ LRs     ]

I don't know how to write the test case.

jennolsen84/PyTables,gdementen/PyTables,rdhyee/PyTables,mohamed-ali/PyTables,jack-pappas/PyTables,PyTables/PyTables,andreabedini/PyTables,FrancescAlted/PyTables,FrancescAlted/PyTables,jennolsen84/PyTables,rabernat/PyTables,andreabedini/PyTables,rabernat/PyTables,mohamed-ali/PyTables,jack-pappas/PyTables,tp199911/PyTables,gdementen/PyTables,jack-pappas/PyTables,mohamed-ali/PyTables,dotsdl/PyTables,gdementen/PyTables,joonro/PyTables,tp199911/PyTables,tp199911/PyTables,rdhyee/PyTables,joonro/PyTables,jack-pappas/PyTables,dotsdl/PyTables,jack-pappas/PyTables,PyTables/PyTables,dotsdl/PyTables,avalentino/PyTables,rdhyee/PyTables,PyTables/PyTables,dotsdl/PyTables,andreabedini/PyTables,mohamed-ali/PyTables,FrancescAlted/PyTables,joonro/PyTables,jennolsen84/PyTables,tp199911/PyTables,avalentino/PyTables,rdhyee/PyTables,andreabedini/PyTables,jennolsen84/PyTables,avalentino/PyTables,joonro/PyTables,rabernat/PyTables,rabernat/PyTables,gdementen/PyTables