[z-machine] Quetzal files

[David Fillmore]

I'm currently busy trying to add Quetzal support to my interpreter, and I
thought it might be a useful idea to have a standard filename extension
for Quetzal files.

Currently, most interpreters use .sav as an extension, which is
understable, but on Windows this means that a Quetzal file is
indistinguishable from any other saved files. Any Windows interpreter that
wants to use some clever hack to make a double-clicked Quetzal file
automatically open the game it was saved from first has to get past the
fact that the .sav extension may well mean the file will be opened by
another program.

Therefore, I am proposing a standard (not obligatory, obviously) filename
extension of .qtz for Quetzal files.

Opinions, comments and suchlike more than welcome.

--
Fillmore