make Lwt.get_cancel tail-recursive
make Lwt.get_cancel tail-recursive

Ignore-this: 96b858b8d9e7b2b389dd5fd2eee8789e

darcs-hash:20110712162157-c41ad-6ba24245d71ea0545f8d1c13e16b40330cab4110

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