Fix for PhantomNode packing in MSVC

Changed bool to uint32_t in bit fields to have 4-byte packings for 32 bits:
"c++ compilers will allocate bit-fields in memory as follows:
several consecutive bit-field members of the same type will
be allocated sequentially. As soon as a new type needs to be allocated,
it will be aligned with the beginning of the next logical memory block."

References:
- https://msdn.microsoft.com/en-us/library/ewwyfdbe.aspx
- http://stackoverflow.com/questions/308364/c-bitfield-packing-with-bools/308383#308383

include/util/typedefs.hpp

@@ -71,13 +71,10 @@ struct SegmentID
         BOOST_ASSERT(!enabled || id != SPECIAL_SEGMENTID);
     }
 
-    NodeID id : 31;
-    bool enabled : 1;
+    NodeID  id              : 31;
+    std::uint32_t enabled   :  1;
 };
 
-// bit-fields are broken on Windows
-#ifndef _MSC_VER
 static_assert(sizeof(SegmentID) == 4, "SegmentID needs to be 4 bytes big");
-#endif
 
 #endif /* TYPEDEFS_H */