aix: fix setsockopt for multicast options
aix: fix setsockopt for multicast options

On AIX the length of socket options
for multicast and ttl options is not always sizeof(char).

AIX has the same issue as solaris which was fixed under
PR-URL: https://github.com/libuv/libuv/pull/243

This PR extends the fix to cover AIX as well.

PR-URL: https://github.com/libuv/libuv/pull/345
Reviewed-By: Ben Noordhuis <59bd0a3ff43b32849b319e645d4798d8a5d1e889@bnoordhuis.nl>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso