fix(dateFilter): follow the CLDR on pattern escape sequences

When there are two single quotes "''" (quotes for clarification) that are not
part of an escape sequence, then this sequence should be handled as one single
quote. See http://www.unicode.org/reports/tr35/tr35-dates.html#Date_Format_Patterns
second and forth examples

Closes #12839

Author: lgalfaso

src/ng/filter/filters.js

@@ -613,7 +613,7 @@ function dateFilter($locale) {
     forEach(parts, function(value) {
       fn = DATE_FORMATS[value];
       text += fn ? fn(date, $locale.DATETIME_FORMATS, dateTimezoneOffset)
-                 : value.replace(/(^'|'$)/g, '').replace(/''/g, "'");
+                 : value === "''" ? "'" : value.replace(/(^'|'$)/g, '').replace(/''/g, "'");
     });
 
     return text;

test/ng/filter/filtersSpec.js

@@ -421,6 +421,8 @@ describe('filters', function() {
     it('should treat a sequence of two single quotes as a literal single quote', function() {
       expect(date(midnight, "yyyy'de' 'a''dd' 'adZ' h=H:m:saZ")).
                       toEqual("2010de a'dd adZ 12=0:5:8AM-0500");
+      expect(date(midnight, "EEE, MMM d, ''yy")).
+                      toEqual("Fri, Sep 3, '10");
     });
 
     it('should accept default formats', function() {