Allow disabling of URL rewriting for SSML output.

Use libsndfile to write audio files.

Import libsndfile, prepare to use it for writing audio files.

Embed espeak-ng

Add commandline flags.

Output converted webpage.

Partially fix segfaults, enough to continue on.

Still questions remain, and there's broken C APIs exposed.

Switch to C for I/O. FIXME currently segfaults.