Change Word64 type from long long to unsigned long long

The following change is required to solve undefined behavior detected by
UBSan.

    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:17:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:18:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:19:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:20:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:21:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:22:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:23:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:24:22
    405 EventFilter/ESRawToDigi/src/ESUnpacker.cc:25:22

~Word64(0) is -1 and left shifting a negative number is undefined
behavior by C++.

These produce 3645 runtime errors from UBSan on full matrix. That's ~15%
of all detected runtime errors.

Word32 is defined as unsigned type. Keep it consistent and define
Word64 as unsigned long long, thus resolved undefined behavior.

Looking at the code these 64-bit masks are not used outside this package
and they are only used with bitwise and operators. The change should not
have any side effects.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
Merge pull request #5458 from davidlt/eventfilter-ubsan-1

Change Word64 type from long long to unsigned long long