buildroot

xerces: disable build and installation of samples

This commit tweaks the Makefile.in to not build and install example
applications.

[Thomas: improve commit log, rebase on top of latest master.]

Signed-off-by: Damien Lanson <damien@kal-host.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>