Reduce http_resp_size to 8k on 32 bit

http_resp_size is allocated on the thread_pool_workspace.  This means
we will hit assert errors if http_resp_size is larger than the
thread_pool_workspace.  8k should be enough in most cases, from a
light sample of web sites in the wild.

bin/varnishd/varnishd.c

@@ -421,6 +421,9 @@ main(int argc, char * const *argv)
 		MCF_ParamSet(cli, "thread_pool_workspace", "16384");
 		cli_check(cli);
 
+		MCF_ParamSet(cli, "http_resp_size", "8192");
+		cli_check(cli);
+
 		MCF_ParamSet(cli, "thread_pool_stack", "32bit");
 		cli_check(cli);