mtr: bump to latest git version (newdns branch)

This fixes the musl build issues and the need to specially patch for
uClibc at the same time. Fixes:
http://autobuild.buildroot.net/results/deb/debeb3ded02c3de63182c3433ff02062192d3fd1/



Also add hash file.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>