Implement recommended file suffixes in dialog
Implement recommended file suffixes in dialog

When creating a file with glk_fileref_create_by_prompt(), there will
be a file filter active for the recommended file extension. For
fileusage_InputRecord and fileusage_Transcript, there will also be a
filter for text/plain files selectable. In any case there is also an
"All files" filter selectable.

wmvanvliet/Chimara,wmvanvliet/Chimara,wmvanvliet/Chimara,wmvanvliet/Chimara,wmvanvliet/Chimara