[FIX] point_of_sale: fix forward port related issues

Fix 697739d, 682e660, da9275a and 697739d which where forward-ported in
8b4f052a38.

addons/point_of_sale/static/src/js/gui.js

@@ -8,6 +8,7 @@ odoo.define('point_of_sale.gui', function (require) {
 
 var core = require('web.core');
 var Model = require('web.DataModel');
+var formats = require('web.formats');
 
 var _t = core._t;
 
@@ -411,8 +412,8 @@ var Gui = core.Class.extend({
     numpad_input: function(buffer, input, options) { 
         var newbuf  = buffer.slice(0);
         options = options || {};
-        var newbuf_float  = instance.web.parse_value(newbuf, {type: "float"}, 0);
-        var decimal_point = instance.web._t.database.parameters.decimal_point;
+        var newbuf_float  = formats.parse_value(newbuf, {type: "float"}, 0);
+        var decimal_point = _t.database.parameters.decimal_point;
 
         if (input === decimal_point) {
             if (options.firstinput) {

addons/point_of_sale/static/src/js/popups.js

@@ -205,7 +205,7 @@ var NumberPopupWidget = PopupWidget.extend({
         this._super(options);
 
         this.inputbuffer = '' + (options.value   || '');
-        this.decimal_separator = instance.web._t.database.parameters.decimal_point;
+        this.decimal_separator = _t.database.parameters.decimal_point;
         this.renderElement();
         this.firstinput = true;
     },

addons/point_of_sale/static/src/js/screens.js

@@ -1706,7 +1706,7 @@ var PaymentScreenWidget = ScreenWidget.extend({
             'title': tip ? _t('Change Tip') : _t('Add Tip'),
             'value': self.format_currency_no_symbol(value),
             'confirm': function(value) {
-                order.set_tip(instance.web.parse_value(value, {type: "float"}, 0));
+                order.set_tip(formats.parse_value(value, {type: "float"}, 0));
                 self.order_changes();
                 self.render_paymentlines();
             }