osmo: minor msvc fixes for bladerf_common.h

lib/bladerf/bladerf_common.h

@@ -31,6 +31,7 @@
 #include <boost/assign.hpp>
 #include <boost/format.hpp>
 #include <boost/lexical_cast.hpp>
+#include <boost/weak_ptr.hpp>
 
 #include <gnuradio/thread/thread.h>
 #include <gnuradio/gr_complex.h>
@@ -40,6 +41,11 @@
 #include "osmosdr/ranges.h"
 #include "arg_helpers.h"
 
+#ifdef _MSC_VER
+#include <cstddef>
+typedef ptrdiff_t ssize_t;
+#endif //_MSC_VER
+
 typedef boost::shared_ptr<struct bladerf> bladerf_sptr;
 
 class bladerf_common