Bug#29957969 QUERY INVOLVING &, <, AND AND OPERATORS COMPUTES INCORRECT RESULT

Bitwise operations on integer values have unsigned result.
The problem occurs whenever these results are cached as Item_cache_int
in a float context. Item_cache_int::val_real() would convert a large
unsigned value to negative double.

The fix is to observe unsigned_flag in Item_cache_int::val_real()

Change-Id: I217f17a81a36ce8ba0d474056eac4bbffee43724