avi2mp4.sh: Konvertiert Dateien nach MP4 (H264 o. XviD/AAC)

1.1.12:
        - added subtitle support (SRT, SUB and VobSub)
        - added $TRACK_LANG so user can set a three digit language code.
          It's not _that_ useful because you can not set it on a
          per-file or even-per track basis. Why did I even add it in the
          first place? :D
        - call MP4Box from within the tmp directory do avoid another bug
          (for some reason MP4Box added something like ".idx" to the
          command line otherwise)
        - some small fixes (comments, README)
        - call MP4Box without "-isma" because it removes the subtitles

1.1.14:
	- now 3GPP text subtitles (.ttxt) are recognized as well
	- new configuration variable SBTL, see README
	- pass TRACK_LANG & video fps along as a global MP4Box argument
	- changed subtitle handling, now for text subtitles the 3GPP
	  header is adapted slightly for proper display (I tried to
	  follow the findings of this blog entry:
	  http://blog.jharding.org/2008/11/subtitles-on-appletv-and-iphone.html
	  Thanks for the ideas!)
	- use "-ipod" argument directly when muxing
1.1.15:
	- fix subtitle related mistake
	- set vim modeline
	- some cleanups (in README as well)

1.1.17:
  - Fixed a few spelling error
  - Changed initial configuration (point out a few differences between PSPs and
    iPods
1.1.18:
  - Fixed the if-block that deals with cropping and updating the aspect ratio
1.1.19:
  - Use wildcard when cleaning up instead of trying to delete file by file
  - Changed default config for PSPs/iPods, apparently x264 changed b frame
    behaviour or default config regarding b frames
  - Substitute some more short command options with long ones
    (wc/bc/grep/renice)
  - Recomplicated track language handling again to fix VobSub track languages
    (these are now determined by MP4Box as it should be); the video track does
    not get a language assigned anymore as that was more or less stupid anyway;
    the language code is now applied only to audio and text subs