syscall: make LoadConnectEx not IPv4-specific on Windows

[linsite]

Calls to Socket in LoadConnectEx always fail with the error
"An address incompatible with the requested protocol was used"
when IPv4 is disabled on Windows. We can work around this by
detecting that specific error and retrying with an IPv6 socket.

Fixes #29759

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Message from Gopher Robot:

Patch Set 1:

(1 comment)

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This PR (HEAD: fb441da) has been imported to Gerrit for code review.

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Message from Lin Lin:

Patch Set 4:

(1 comment)

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