config/functions: retire unused functions

eglibc ceased active development years ago and is no longer in tree, so no need
to check for it.

tolower() has been around since 2010 and is unused anywhere. Wish it well!

Should it return, tr '[:upper:]' '[:lower:]' is likely better.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>

config/functions

@@ -671,17 +671,6 @@ install_addon_files() {
   create_addon_xml "$1"
 }
 
-tolower() {
-  echo "$@" | tr ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz
-}
-
-require_eglibc() {
-  if [ "$TARGET_LIBC" != eglibc ]; then
-    echo "$1 requires eglibc, aborting."
-    exit 1
-  fi
-}
-
 add_user() {
   # Usage: add_user "username" "password" "userid" "groupid" "description" "home" "shell"
   mkdir -p ${INSTALL}/etc