bluez5_utils: new package

This patch adds Bluez 5.x. Its API is not backwards compatible with
BlueZ 4 so it is packaged separately from BlueZ 4.

BlueZ utils will use systemd and/or udev if enabled. It contains a
hook to install the GATT support tool, which is always built but not
installed by default.

[Thomas:
 - Add dependency on 3.4 kernel headers
 - Add options for OBEX support and client support, to make the
   libical and readline dependencies optional.
 - Rewrap Config.in help text.
 - Adapt indentation in .mk file.
 - Bump to version 5.21.
 - Use BR2_PACKAGE_HAS_UDEV instead of BR2_PACKAGE_UDEV.]

Signed-off-by: Marcin Bis <marcin@bis.org.pl>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>