Added extern "C" declaration for C++ compatibility

include/libssh2.h

@@ -38,6 +38,10 @@
 #ifndef LIBSSH2_H
 #define LIBSSH2_H 1
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stddef.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -384,4 +388,8 @@ LIBSSH2_API LIBSSH2_CHANNEL *libssh2_scp_send_ex(LIBSSH2_SESSION *session, const
 
 LIBSSH2_API int libssh2_base64_decode(LIBSSH2_SESSION *session, char **dest, int *dest_len, char *src, int src_len);
 
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
 #endif /* LIBSSH2_H */