In ancient MinGW versions, in6addr_any was declared as extern, but not
defined. Because of that, 22a0c57746 added
definitions for in6addr_any when compiling with MinGW. The bug was fixed in
w32api version 3.6 from 2006, so this workaround is not needed anymore for
recent versions.
This fixes the following MinGW-w64 warnings because the MinGW-w64 version of
IN6ADDR_ANY_INIT has the two additional braces inside the macro:
util.c:59:14: warning: braces around scalar initializer
util.c:59:40: warning: excess elements in scalar initializer
Ref: e4803e0da2/tree/w32api/ChangeLog
Closes https://github.com/curl/curl/pull/1379
55f4ababde