First we refactor to have only a single usage of `PHP_GAI_STRERROR()`
left; then we drop the macro in favor of calling the different
functions conditionally in an ad-hoc style.
This is necessary because the return value of `php_win32_error_to_msg`
needs to be freed by the caller.
The error messages are no more inline with other error messages, since
`gai_strerror()` apparently always appends a period and a space.
We also properly configure IPv4/v6 on Windows. Since WSPiApi.h has been
created in 2000, so we can safely assume that it is available everywhere
nowadays. Furthermore, `gai_strerror()` is available regardless of
whether there is IPv6 support.
edcd6cc564