lib: trace: Fixed typo in documentation.
lib: trace: warning and error don't show additional info any more.

The two methods warning and error which are supposed to be used to
inform the user of the tool about an error or a warning don't include
filename, function name and line number any more in the output as this
is no valuable information for the user. Just the debug method includes
this information as this method is supposed to be used by developers
which have access to the source code.