[WIP] Additional tests for sorted data interface.
Add tests for save and restore position.
Update locate tests to move cursor to position already passed.
[WIP] Start on tests for advanceTo().
Update tests to appropriately check cursor.locate() return value.

Will return true if and only if the specified key and diskloc were
an exact match.
Comment out tests that fail on mmapv1.

These either trigger an invariant failure or a segmentation fault.
Do a bit more testing of advanceTo().
Make restorePosition() take an OperationContext.
DiskLoc instances must have an even offset for mmapv1.
Change to use distinct disklocs for each entry.

Commented out sections of tests that fail for mmapv1.