[1.2.X] Fixed #14046 -- Made {% include %} behave the same, regardless of...

[1.2.X] Fixed #14046 -- Made {% include %} behave the same, regardless of whether the template included is named by variable or constant string. Thanks to defcube for the report, and George Karpenkov for the draft patch.

Backport of r15413 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15414 bcc190cf-cafb-0310-a4f2-bffc1f526a37