Fix leak in "Open Font" dialog file filter list

Each time the "Open Font" dialog is displayed, FVOpenFont() first gets a
list of file filter types from StandardFilters().  The list 'filts' is
later used in setting up the dialog, but is nowhere free()d.  About 2K
bytes leaks on each dialog use.

This fix free()s the list using the magic routine GTextInfoArrayFree().
Merge pull request #1608 from tshinnic/leak_openfontdlg_filesfilter

Fix leak in "Open Font" dialog file filter list