procd: update procd.sh to disallow signal-numbers, enforce signal-names

A given signal-name is now converted to the corresonding number. In general
it's good style to use names (readability) and it's more portable: signal
numbers can be architecture-dependent, so we are more safe giving names.

A real world example is signal 10, which is BUS on ramips and USR1 on PPC.

All users of 'procd_send_signal' must change their code to reflect this.

Signed-off-by: Bastian Bittorf <bb@npl.de>

package/system/procd/files/procd.sh

@@ -213,9 +213,12 @@ _procd_set_param() {
 			json_add_string "" "$@"
 			json_close_array
 		;;
-		nice|reload_signal)
+		nice)
 			json_add_int "$type" "$1"
 		;;
+		reload_signal)
+			json_add_int "$type" $(kill -l "$1")
+		;;
 		pidfile|user|seccomp|capabilities)
 			json_add_string "$type" "$1"
 		;;