Backport !1827 “Windows: fix FD_READ condition flag still set on recoverable UDP socket errors.” to glib-2-66

Contrary to what the WSARecvFrom seem to imply, a UDP socket is perfectly recoverable and usable after a WSAECONNRESET error (and, I assume, WSAENETRESET). However GSocket condition has the FD_READ bit set after a UDP socket fails with WSAECONNRESET, even if no data is available on the socket anymore; this causes select calls to report the socket as readable when, in fact, it's not.

The change resets FD_READ flag on a socket upon the above error conditions; there's no 'if' to filter between datagram and stream sockets as the change should be harmless in the case of stream sockets which are, however, very unlikely to be usable after a WSAECONNRESET.

Trivial backport of !1827 (merged) to glib-2-66.

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