gmacros: Prioritize the usage of [[noreturn]] in C++11

We defined G_NO_RETURN as [[noreturn]] in the C++ case, but only after
trying the __attribute__ syntax, so it was never used in GNUC compatible
compilers.

Give it priority instead when supporting a C++11 compiler and onwards.

As per this we need to adapt the code in the places where it was not
properly used (leading to compilation warnings).

glib/gtestutils.h

@@ -541,8 +541,8 @@ void    g_assertion_message             (const char     *domain,
                                          int             line,
                                          const char     *func,
                                          const char     *message) G_ANALYZER_NORETURN;
-GLIB_AVAILABLE_IN_ALL
 G_NORETURN
+GLIB_AVAILABLE_IN_ALL
 void    g_assertion_message_expr        (const char     *domain,
                                          const char     *file,
                                          int             line,