added proper headers to source files

lib/aaa_errors.sh

@@ -1,5 +1,12 @@
+# ------------------------------------------------------------------------------
 # Error management functions
-
+# Copyright (c) 2019-2021 Geoffray Levasseur <fatalerrors@geoffray-levasseur.org>
+# ------------------------------------------------------------------------------
+# This file is distributed under 3-clause BSD license.
+# The complete license agreement can be obtained at:
+# https://opensource.org/licenses/BSD-3-Clause
+# ------------------------------------------------------------------------------
+ 
 # Exit with error
 function die()
 {
@@ -63,6 +70,7 @@ function backtrace
     echo "=============================="
 }
 
+# Test and exit if not root (or any UID 0 user)
 check_root()
 {
     [[ $NO_ROOT_CHECK == true ]] && return 0