Changes:
* Date and Timestamp are now distinct with all Dates before all Timestamps.
* Numeric comparisons now correctly handle Doubles and Long > 2**53.
* CodeWScope doesn't strcmp BSONObjs or strings which may contain NULs.
There should be no changes in any of the cases where woCompare defined a
correct total ordering before. The new behavior matches the ordering defined
by KeyString.
Related tickets:
* SERVER-3304 Error comparing Date and Timestamp
* SERVER-3719 Total ordering over Longs and Doubles
* SERVER-7804 CodeWScope comparisons are broken
* SERVER-16632 Change WiredTiger index key format
Changes to the comparison function for aggregation will be handled separately
as SERVER-16708.
