Use all arguments to AC_PREREQ and AC_INIT
About dialog: use en dash to indicate a range
Update documentor credits
Use a single button for play, pause, and restart
Move scores dialog to a separate file
Hint time penalty now increases

The initial hint costs 10s as before. But each successive hint will cost
10s more than the last, to a max of 60s.

These constants aren't really playtested beyond the observation that a
flat 10s is much too low.
Properly add score-dialog.vala

Oh how embarrassing!
Do not show the empty buttons sidebar on the new game dialog. https://bugzilla.gnome.org/show_bug.cgi?id=712702