100% Match of MxDSFile (#51)

* 100% Match of MxDSFile

* ...almost, MxDSFile::Open is still not quite matching but all of the
  other methods are 100% matching.

* Turns out that most of the virtual methods and some of the members are
  actually on the MxDSSource base class, which I've pulled out as part
  of this.

* In order to implement the methods I added the MXIOINFO class, which
  seems to be a thin wrapper around the MMIOINFO windows structure. We
  can tell this because MMIOINFO::~MMIOINFO was included in the DLL
  exports, and calls down to a function which deconstructs something
  looking exactly like MMIOINFO.

* Add mxdssource.cpp

* mattkc feedback

* some accuracy improvements

* Use FOURCC macro

* Tirival solve in mxioinfo.cpp

* Update mxdsfile.cpp

0xFFFFFFFF -> -1

---------

Co-authored-by: Christian Semmler <mail@csemmler.com>

LEGO1/mxdssource.h

@@ -0,0 +1,30 @@
+#ifndef MXDSSOURCE_H
+#define MXDSSOURCE_H
+
+#include "mxcore.h"
+
+class MxDSSource : public MxCore
+{
+public:
+  MxDSSource()
+    : m_lengthInDWords(0)
+    , m_pBuffer(0)
+    , m_position(-1)
+  {}
+
+  virtual long Open(unsigned long) = 0;
+  virtual long Close() = 0;
+  virtual void SomethingWhichCallsRead(void* pUnknownObject);
+  virtual long Read(unsigned char *, unsigned long) = 0;
+  virtual long Seek(long, int) = 0;
+  virtual unsigned long GetBufferSize() = 0;
+  virtual unsigned long GetStreamBuffersNum() = 0;
+  virtual long GetLengthInDWords();
+
+protected:
+  unsigned long m_lengthInDWords;
+  void* m_pBuffer;
+  long m_position;
+};
+
+#endif // MXDSSOURCE_H