hdf5_msb

[svn-r8491] Purpose:  Bug fix

Description:  For certain compiler(PGI we know so far), during conversion
from float or double to unsigned long long, it does round-up when the
fraction part is greater than 0.5, which shouldn't happen.

Solution:  check it during configuration and compensate this offset
during testing in dtypes.

Platforms tested:  verbena and fuss.  verbena is the only machine with
PGI compiler. Ran it on fuss to verify it with other compiler.