Add debug on alterTable (#46)

Author: Sakib Hasan

lib/migration.js

@@ -6,6 +6,7 @@
 'use strict';
 
 var async = require('async');
+var debug = require('debug')('loopback:ibmdb');
 
 module.exports = function(IBMDB) {
   IBMDB.prototype.showFields = function(model, cb) {
@@ -249,6 +250,8 @@ module.exports = function(IBMDB) {
 
   IBMDB.prototype.alterTable = function(model, actualFields, actualIndexes,
   callback, checkOnly) {
+    debug('IBMDB.prototype.alterTable %j %j %j %j',
+           model, actualFields, actualIndexes, checkOnly);
     var self = this;
     var sql = [];
     var tasks = [];