mpv: improve BUILD, bump REVISION due to libass update.
mpv: improve BUILD, bump REVISION due to libass update.

* Do not call bootstrap.py because it downloads waf-1.8.12 in BUILD!
  Instead, add a SOURCE_URI_2 for waf-1.8.12 and mimic bootstrap.py.
* Use tar.gz (instead of zip) in SOURCE_URI. (identical contents)
* Add SOURCE_FILENAME. (v0.23.0.tar.gz -> mpv-0.23.0.tar.gz)
* Drop unneeded SOURCE_DIR.
* Switch HOMEPAGE to https.

moochris/haikuports,haikuports/haikuports,nielx/haikuports,koletzky/haikuports,miqlas/haikuports,miqlas/haikuports,Begasus/haikuports,haikuports/haikuports,moochris/haikuports,miqlas/haikuports,Begasus/haikuports,haikuports/haikuports,moochris/haikuports,nielx/haikuports,haikuports/haikuports,haikuports/haikuports,Begasus/haikuports,nielx/haikuports,koletzky/haikuports,koletzky/haikuports,Begasus/haikuports,Begasus/haikuports