Log Message:
Update to 2.22
- fix memory leaks in st-icu.cc
- for st-swath, don't spawn new process for every stdin readline

  pthai.el:
- clean up pthai-unknown* funcs and add toggle to highlight unknown words
- add option to use external processes for swath and icu which is
  faster and gives more split choices
- add pause and pthai-no-audio-pause-length custom setting for pausing
  on words with no audio when attempting audio play
- clean-ups for pthai-currency* functions
- consolidate text highlighting into pthai-highlight-on/off functions
- when reloading pthai.el library, don't clear 'pthai-dictionary