fixes to build libnodave and use it on Linux

[zati-]

• fixees to libnodave code to compile correctly with gcc in linux
• fix to Makefile to build libnodave in linux
• fixes to libnodave p/invoke to correctly call libnodave functions

[jogibear9988]

I don't get what this is about?
It was intentionally changed to Intptr, so the lib could used on 32 and 64 bit systems.
So I don't get why you would change this.

[zati-]

Linux definition in nodave.h for dost structure is

#ifdef LINUX
#define DECL2
#define EXPORTSPEC
	typedef struct dost {
		int rfd;
		int wfd;
		//    int connectionType;
	} _daveOSserialType;
#include <stdlib.h>
#define tmotype int
#define OS_KNOWN	// get rid of nested ifdefs.
#endif    

so it's always 32 bits.

[jogibear9988]

Then maybe this needs to be fixed? The other changes I could not merge, i need 64 bit windows support