elfutils: new package

This patch adds a a package for elfutils. For now, the package is
glibc specific, as adding uClibc support for this package is quite
tedious, and will therefore be done through followup patches.

Heavily based from work done by Stefan Fröberg, but with many further
modifications by Thomas Petazzoni.

Signed-off-by: Stefan Fröberg <stefan.froberg@petroprogram.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>