Stub out missing translations according to language plurals.

lib/po.js

@@ -114,7 +114,9 @@ PO.parse = function (data) {
         }
     });
 
-    var item = new PO.Item();
+    var parsedPluralForms = PO.parsePluralForms(po.headers['Plural-Forms']);
+    var nplurals = parsedPluralForms.nplurals;
+    var item = new PO.Item({ nplurals: nplurals });
     var context = null;
     var plural = 0;
     var obsoleteCount = 0;
@@ -128,7 +130,7 @@ PO.parse = function (data) {
             obsoleteCount = 0;
             noCommentLineCount = 0;
             po.items.push(item);
-            item = new PO.Item();
+            item = new PO.Item({ nplurals: nplurals });
         }
     }
 
@@ -234,7 +236,26 @@ PO.parse = function (data) {
     return po;
 };
 
-PO.Item = function () {
+PO.parsePluralForms = function (pluralFormsString) {
+    var results = (pluralFormsString || '')
+        .split(';')
+        .reduce(function (acc, keyValueString) {
+            var trimmedString = keyValueString.trim();
+            var equalsIndex = trimmedString.indexOf('=');
+            var key = trimmedString.substring(0, equalsIndex).trim();
+            var value = trimmedString.substring(equalsIndex + 1).trim();
+            acc[key] = value;
+            return acc;
+        }, {});
+    return {
+        nplurals: results.nplurals,
+        plural: results.plural
+    };
+};
+
+PO.Item = function (options) {
+    var nplurals = options && options.nplurals;
+
     this.msgid = '';
     this.msgctxt = null;
     this.references = [];
@@ -244,6 +265,8 @@ PO.Item = function () {
     this.extractedComments = [];
     this.flags = {};
     this.obsolete = false;
+    var npluralsNumber = Number(nplurals);
+    this.nplurals = (isNaN(npluralsNumber)) ? 2 : npluralsNumber;
 };
 
 PO.Item.prototype.toString = function () {
@@ -316,10 +339,21 @@ PO.Item.prototype.toString = function () {
     ['msgctxt', 'msgid', 'msgid_plural', 'msgstr'].forEach(function (keyword) {
         var text = self[keyword];
         if (text != null) {
+            var hasTranslation = false;
+            if (Array.isArray(text)) {
+                hasTranslation = text.some(function (text) {
+                    return text;
+                });
+            }
+
             if (Array.isArray(text) && text.length > 1) {
                 text.forEach(function (t, i) {
                     lines = lines.concat(mkObsolete + _process(keyword, t, i));
                 });
+            } else if (self.msgid_plural && keyword === 'msgstr' && !hasTranslation) {
+                for (var pluralIndex = 0; pluralIndex < self.nplurals; pluralIndex++) {
+                    lines = lines.concat(mkObsolete + _process(keyword, '', pluralIndex));
+                }
             } else {
                 var index = (self.msgid_plural && Array.isArray(text)) ?
                     0 :