use rlim_cur instead of rlim_max

(it seems rlim_max is unreliable on some systems and anyway
 as a userspace program, not trying to raise the limit, we should
 honor the soft limit and not the hard one)

src/iomux.c

@@ -139,7 +139,7 @@ iomux_create(int bufsize, int threadsafe)
 
     struct rlimit rlim;
     if (getrlimit(RLIMIT_NOFILE, &rlim) == 0) {
-        iomux->maxconnections = rlim.rlim_max;
+        iomux->maxconnections = rlim.rlim_cur;
     } else {
         fprintf(stderr, "Can't get the max number of filedescriptors: %s\n",
                 strerror(errno));