add_suffix

Adds a suffix match rule to a filter.

This is similar to adding a match for the pattern "*.suffix"

An exaple to filter files with the suffix ".sub": ```c gtk_file_filter_add_suffix (filter, "sub"); ```

Filters with multiple dots are allowed.

In contrast to pattern matches, suffix matches are *always* case-insensitive.

Parameters:

this	a file filter
suffix	filename suffix to match