Andreas Mieke authored Aug 03, 2015 and Philipp Schafft committed Sep 05, 2015

This commit adds a function to check the validity of the icecast.xml
configuration file. The function returns 0 if the file is valid, -1 if
there was an unknown error or error codes as defined in
xmlRelaxNGValidErr.

TODO:
* Add  the schema somewhere into the repository where it makes sense.
* Use the function to validate the configuration file and add handling
for invalid configuration files.