fix style selection menu displays styles twice

When the doctype reference in a style definition matched public id and
system id of a doctype, the style was displayed twice in the styles
menu.

Change-Id: I846e9ad5d158c074c8e1e054809a0b50dc05fdf6
Signed-off-by: Carsten Hiesserich <carsten.hie@gmail.com>
4 files changed