Cumulative changes required to enable / ease compilation in Linux with gcc. (PR #861)

Split MouseInterface to isolate DirectInput code.
Avoid overflow in platforms where RAND_MAX is a big integer constant.
Fix include files for gcc (where enums cannot be forward declared).

source/MouseInterface.h

@@ -107,10 +107,3 @@ protected:
 
 	SyncEvent m_syncEvent;
 };
-
-namespace DIMouse
-{
-	HRESULT DirectInputInit( HWND hDlg );
-	void DirectInputUninit( HWND hDlg );
-	HRESULT ReadImmediateData( long* pX=NULL, long* pY=NULL );
-};