BaseTools: Unify long and int in Expression.py

BaseTools: Unify long and int in Expression.py

Per PEP237(*), 'long' is unified with 'int' and removed from python3.

* To make the script compatible with both python2 and python3,
  'type(0L)' is replaced with 'type(sys.maxsize + 1)'. In python2,
  the number is 'long', while it's 'int' in python3. We can remove
  the workaround after moving to python3 completely.

* long() is replaced with int() since int() returns a long when need.

(*) https://www.python.org/dev/peps/pep-0237/

Contributed-under: TianoCore Contribution Agreement 1.1
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>