* ext/socket/rubysocket.h, ext/socket/unixsocket.c,
  ext/socket/ancdata.c: Use HAVE_STRUCT_MSGHDR_MSG_CONTROL instead
  of HAVE_ST_MSG_CONTROL.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40623 b2dd03c8-39d4-4d8f-98ff-823fe69b080e