Fix for docdir issue with deb/RPM. Fixes #2121

Replaced docdir with otherdocdir and made it relative to docdir.
This seems to work for debian and plain make install.
Will test RPM later.
NEWS updated for 2.4.0 and 2.4.1
Cleanup: make strcmp() more explicit in _start_logging()

This avoids if(strcmp()) constructs in favor of if(strcmp() == 0)
constructs. This is aligned with coding style and will improve
readability of the code.

Thanks to miksago. closes #2102
Some minor changes, added Opus and WebM

see #2122
Small changes. see #2122
Another small edit. refs #2122
YAC - yet another change. ref #2122
Regression Fix: Correction of old-style <authentication>.

Old-style <authentication> within <mount> didn't work for type="url"
as well as some other parameters due to confusion between "node"
and "child" variable.

Thanks for trilliot for pointing out! Should work now.
closes #2039
adding one url. refs #2122
Merge branch 'master' of ssh://git.xiph.org/icecast-server
last missing url. refs #2122
Merge branch 'master' of ssh://git.xiph.org/icecast-server
Incremental README improvement. refs #2122
Fix: Send Content-Disposition:-header correctly, closes #1953
Feature: Support command line arguments in <event type="exec">

This adds support to pass additional command line parameters
to called processes. closes #1752
Fix: Fixed compiler warnings

This fixes some compiler warnings. The code should be warning free
if gcc with -Wall is used but for the following:
{{{
admin.c: In function 'command_manageauth':
admin.c:790: warning: unused variable 'mountinfo'
}}}
This warning is due <role> migration. See #2123 for more details on
this warning. Please test with care. closes 2063