snprintf and ssize_t not defined

[mojca]

Under Visual Studio 2012 I had to remove #include <unistd.h> and replace it with

#if defined(_MSC_VER)
#include <BaseTsd.h>
typedef SSIZE_T ssize_t;
#define snprintf _snprintf
#include <io.h>
#endif

to get the code from source/geometry/src/GateDMapVol.cc and GateDMaplongvol.cc to compile. The code needs to be reviewed.