Add Lucarda's flite, which replaces moocow/flite.

This is the latest version (0.3.2) from
https://github.com/Lucarda/pd-flite, with some very minor touches to
make the source compile with the latest gcc versions.

Lucarda's flite is much newer than the one which comes with our moocow
version. It's also self-contained (CMU flite is included),
cross-platform (moocow/flite only works on Linux and requires 3rd party
libraries), and has useful additional functionality like multi-threading
support and the ability to load different voices.