add syntax to api structures, use them for usage returns, do more checking on valid usage and cleanup some output of api commands.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@3001 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/applications/mod_dptools/mod_dptools.c

@@ -33,7 +33,6 @@
 
 static const char modname[] = "mod_dptools";
 
-
 static void transfer_function(switch_core_session_t *session, char *data)
 {
 	int argc;
@@ -133,7 +132,7 @@ static switch_api_interface_t dptools_api_interface = {
 	/*.interface_name */ "strftime",
 	/*.desc */ "strftime",
 	/*.function */ strftime_api_function,
-	/*.syntax */ NULL,
+	/*.syntax */ "strftime <format_string>",
 	/*.next */ NULL
 };