C++ binding: Fixup memory leak in input module receive() calls

The Input::send() method allocated glib strings and copied input data,
but only released the glib string container and leaked the actual string
content. This led to leaks in the size of the verbatim input file, which
is especially wasteful for uncompressed textual representations.

This fixes bug #976.

bindings/cxx/classes.cpp

@@ -1407,7 +1407,7 @@ void Input::send(void *data, size_t length)
 {
 	auto gstr = g_string_new_len(static_cast<char *>(data), length);
 	auto ret = sr_input_send(_structure, gstr);
-	g_string_free(gstr, false);
+	g_string_free(gstr, true);
 	check(ret);
 }