Fixed #15157 -- Modified evaluation of literals surrounded by _(' and ')' in...

Fixed #15157 -- Modified evaluation of literals surrounded by _(' and ')' in templates to be evaluated at render time instead of at compile time by using ugettext_lazy. Thanks Jonathan S for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15327 bcc190cf-cafb-0310-a4f2-bffc1f526a37