Fix big with enums OR operation in Python 3 (#222)

The bug can be reproduced using such code:
```
pwndbg> py import re; re.DOTALL | re.MULTILINE
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.6/enum.py", line 794, in __or__
    result = self.__class__(self._value_ | self.__class__(other)._value_)
  File "/usr/lib/python3.6/enum.py", line 291, in __call__
    return cls.__new__(cls, value)
  File "/usr/lib/python3.6/enum.py", line 533, in __new__
    return cls._missing_(value)
  File "/usr/lib/python3.6/enum.py", line 760, in _missing_
    new_member = cls._create_pseudo_member_(value)
  File "/usr/lib/python3.6/enum.py", line 786, in _create_pseudo_member_
    pseudo_member._name_ = None
AttributeError: 'int' object has no attribute '_name_'
Error while executing Python code.
```

The fix seems to work with Python 2 as well:
http://asciinema.org/a/czopcwobjwt2dk9vzif0zk49u

pwndbg/inthook.py

@@ -18,18 +18,20 @@ from future.utils import with_metaclass
 
 import pwndbg.typeinfo
 
-if sys.version_info < (3,0):
+if sys.version_info < (3, 0):
     import __builtin__ as builtins
 else:
     import builtins
 
 _int = builtins.int
 
+
 # We need this class to get isinstance(7, xint) to return True
 class IsAnInt(type):
     def __instancecheck__(self, other):
         return isinstance(other, _int)
 
+
 class xint(with_metaclass(IsAnInt, builtins.int)):
     def __new__(cls, value, *a, **kw):
         if isinstance(value, gdb.Value):
@@ -37,11 +39,16 @@ class xint(with_metaclass(IsAnInt, builtins.int)):
                 value = value.cast(pwndbg.typeinfo.ulong)
             else:
                 value = value.cast(pwndbg.typeinfo.long)
-        if isinstance(value, gdb.Symbol):
+
+        elif isinstance(value, gdb.Symbol):
             symbol = value
-            value  = symbol.value()
+            value = symbol.value()
             if symbol.is_function:
                 value = value.cast(pwndbg.typeinfo.ulong)
+
+        else:
+            return _int.__new__(cls, value, *a, **kw)
+
         return _int(_int(value, *a, **kw))
 
 # Do not hook 'int' if we are just generating documentation
@@ -49,6 +56,6 @@ if os.environ.get('SPHINX', None) is None:
     builtins.int = xint
     globals()['int'] = xint
 
-    if sys.version_info >= (3,0):
+    if sys.version_info >= (3, 0):
         builtins.long = xint
         globals()['long'] = xint