implemantations.

It is unclear why the two implementations differ.

we currently only support 22050 as samplerate so this code has no
effect. This should be readded to setSpeed() with and without Sonic if
multiple samplerates are supported in the future.

There are two SetSpeed(), one for Sonic and one without. The differences
are very small.

In SetSpeedMods(), sample rate is adjusted for Sonic only:
 speed.min_sample_len = (speed.min_sample_len * samplerate_native) / 22050;

Since samplerate_native is 22050 at the moment this line has no effect.

speed.fast_settings[] was introduced in 7b2eecc724 to be used with
Sonic. Looks like after 7b2eecc724 the code related to everything
except fast_settings[0] was removed.

Might be that speed.fast_settings[0] is also irrelevant and could be
removed.

It is set but never used.

Moved include/espeak/speak_lib.h to include/espeak-ng/speak_lib.h and
created a symlink from the original location.

This commit has been reported to cause distortions in phoneme
pitches and speeds.

Also use size_t instead of int in some places
where it make sense

This allows newer versions of sonic to be used and to keep
up-to-date with bug fixes provided by the system.