termux-tools: Add su wrapper

packages/termux-tools/su

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+if [ -x /system/xbin/su ]; then
+	/system/xbin/su $@
+else
+	echo "There is no su program on this device. Termux"
+	echo "does not supply tools for rooting, see e.g."
+	echo "http://www.androidcentral.com/root for"
+	echo "information about rooting Android."
+	exit 1
+fi