Fix warning anywhere netwrap.h is included before sockwrap.h

sbbs3/../xpdev/netwrap.h:45:27: warning: 'parseIPv6Address' has C-linkage specified, but returns incomplete type 'struct in6_addr' which could be incompatible with C [-Wreturn-type-c-linkage]
DLLEXPORT struct in6_addr parseIPv6Address(const char*);
                          ^