logging in gtkdoc tools

[Stefan Kost <ensonic hora-obscura de>]

hi,

any objections if I replace all the print-statements in the gtkdoc tools
with respactive Log::Log4perl statements. Means we grow a dependency. On
the other hand this look like beeing quite useful for developers.

Recommended reading:
http://log4perl.sourceforge.net/
http://www.perl.com/pub/a/2002/09/11/log4perl.html?page=1

Ciao
  Stefan