include signal.h in lwt_unix_stubs.c (for SIGWINCH)
include signal.h in lwt_unix_stubs.c (for SIGWINCH)

Ignore-this: b15754e4fa443ea07ef73d31ba8b99ef

darcs-hash:20100106131913-c41ad-fecb3c8fcc79cff3eb366e37fdb116a5268dec48

fdopen/lwt,rgrinberg/lwt,rneswold/lwt,mfp/lwt,rgrinberg/lwt,ocsigen/lwt,rneswold/lwt,c-cube/lwt,fdopen/lwt,gfxmonk/lwt,ocsigen/lwt,rgrinberg/lwt,c-cube/lwt,c-cube/lwt,ocsigen/lwt,janestreet/lwt-async,gfxmonk/lwt,mirage/lwt,janestreet/lwt-async,mirage/lwt,rneswold/lwt,mfp/lwt,rgrinberg/lwt