Does anyone remember (or know) why the config.h generated by the slony 
configure defines

  HAVE_POSIX_SIGNALS

Do don't seem to use it in the slony source.
PG 9.4 defines this in the pg_config.h headers so we get multiple define 
warnings when we build slony against 9.4

Can we just remove the define it from config.h.in  (but leave the check 
in libc.m4 as is) ?