Define glib_typeof with C++11 decltype()
This reinstate reverted commit from !1575 (merged) with the extra typename
that should fix regression in GJS. It also contains commits from !1703 (closed) that got closed.
This reinstate reverted commit from !1575 (merged) with the extra typename
that should fix regression in GJS. It also contains commits from !1703 (closed) that got closed.