dict.cc.py: Update comment
dir.sh: Fix printing of usage help

Every shell script gets its own name as an argument, so $# is always
greater or equal to 1.
dir.sh: Replace ls with find

Be more robust against weird file names. Also replace `echo` with
`printf` since the formers behaviour is implementation-defined with
<backslash> in its arguments.

Also remove -w option, because we automatically change into the
directory for which the listing is generated and so every link from path
from find starts with `./`.

Problems:
- we cannot print file mtime anymore with find.
- IFS still includes <space> and so file names with trailing spaces get
  truncated

http://www.dwheeler.com/essays/fixing-unix-linux-filenames.html
dir.sh: Change arguments for output_listing()

Also: exchange more variable expansoin on command argument lists with
heredocs to avoid argument list limits.
chvol: Add option to play sound

The new option `-s` invokes a programm to play a sound whenever the
script is invoked. I use this to play a click sound to know how high the
volume is (this is how it is in Mac OS X).