Thanks to the previous commit, a modifier key can now be more complex
than just a KeyValue.Modifier. This allows a more elegant implementation
of the compose key, that could be taken as a base for other features
(eg. unicode hex entry, hangul)
The COMPOSE_PENDING modifier is removed as keys of kind Compose_pending
can act as a modifier. This has the advantage of highlighting the key
that was last pressed in the sequence.
Rules are added to Pointers: Non-special but latchable keys must clear
latches and cannot be locked with a long press. These rules were not
needed before but were intended.
compile.py implements a parser for X11's Compose.pre files. A lot of
code is necessary to interpret character names but thanksfully, the name
of most characters is contained in the file.
The state machine is compiled into two char arrays which unfortunately
requires an expensive initialisation and allocation.
The COMPOSE_PENDING modifier indicate whether a compose sequence is in
progress. The new key of kind Compose_pending sets the current state of
the sequence.
The compose sequences are compiled into a state machine by a python
script into a compact encoding.
The state of the pending compose is determined by the index of a state.
