[1.2.X] Fixed #11206 -- Ensure that the floatformat template filter doesn't...

[1.2.X] Fixed #11206 -- Ensure that the floatformat template filter doesn't switch to scientific notation when asked to format a zero value with more than six decimal places. Thanks Tai Lee for the report and fix and Facundo Batista for his help when Decimal module expertise was needed.

Backport of [15736] from trunk

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15738 bcc190cf-cafb-0310-a4f2-bffc1f526a37