Fix escape representation of non-printable characters

[drepper]

The avahi_escape_label function generates a string which uses an escape sequence to represent non-printable characters. The representation used does not conform to shell/C/… rules, though. It uses a zero-padded decimal representation. A space = U+0020 character is therefore printed as \032. In shell/C/… strings this represents U+001a. At least for me this is highly confusing and I questioned my settings.

Therefore I suggest to use the traditional octal representation.