Define MxLong/MxULong (#71)

* define MxLong/MxULong

The "long" type has different sizes on different platforms, and this may cause issues.

* use DWORD to match RegQueryValueExA arg

LEGO1/mxdssource.cpp

@@ -8,7 +8,7 @@ void MxDSSource::SomethingWhichCallsRead(void* pUnknownObject)
 }
 
 // OFFSET: LEGO1 0x100bfff0
-long MxDSSource::GetLengthInDWords()
+MxLong MxDSSource::GetLengthInDWords()
 {
   return m_lengthInDWords;
 }