Use 'true' and 'false' in sk_set_frozen calls.

Apparently a handful of calls to that particular function managed to
miss my big-bang conversion to using bool where appropriate, and were
still being called with constants 0 and 1.

sshshare.c

@@ -1940,7 +1940,7 @@ static int share_listen_accepting(Plug *plug,
         return err != NULL;
     }
 
-    sk_set_frozen(cs->sock, 0);
+    sk_set_frozen(cs->sock, false);
 
     add234(cs->parent->connections, cs);