[Chromoting] Add version stamps to Mac installer and host scripts.

remoting/host/installer/mac/Scripts/remoting_preflight.sh

Index: remoting/host/installer/mac/Scripts/remoting_preflight.sh
===================================================================
--- remoting/host/installer/mac/Scripts/remoting_preflight.sh	(revision 138115)
+++ remoting/host/installer/mac/Scripts/remoting_preflight.sh	(working copy)
@@ -4,6 +4,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+# Version = @@VERSION@@
+
 HELPERTOOLS=/Library/PrivilegedHelperTools
 NAME=org.chromium.chromoting
 CONFIG_FILE="$HELPERTOOLS/$NAME.json"
@@ -19,6 +21,8 @@
   exit 0
 }
 
+logger Running Chrome Remote Desktop preflight script @@VERSION@@
+
 # If there is an _enabled file, rename it while upgrading.
 if [[ -f "$ENABLED_FILE" ]]; then
   mv "$ENABLED_FILE" "$ENABLED_FILE_BACKUP"