Set default value of cm_alloc_size to 2MB.

btpd/opts.c

@@ -11,4 +11,4 @@ unsigned net_max_peers;
 unsigned net_bw_limit_in;
 unsigned net_bw_limit_out;
 int net_port = 6881;
-off_t cm_alloc_size = 2048;
+off_t cm_alloc_size = 2048 * 1024;