libssh2.h: Fix Error C2371 'ssize_t': redefinition
Closes
@@ -137,8 +137,9 @@ typedef __int64 int64_t;
typedef unsigned __int64 uint64_t;
typedef unsigned __int64 libssh2_uint64_t;
typedef __int64 libssh2_int64_t;
-#ifndef ssize_t
+#if (!defined(HAVE_SSIZE_T) && !defined(ssize_t))
typedef SSIZE_T ssize_t;
+#define HAVE_SSIZE_T
#endif
#else
#include <stdint.h>
