mpd: add patch to fix build failures

mpd is using snprintf without including stdio.h when pthread_setname_np
isn't available leading to failure, hence patch it. Fixes:
http://autobuild.buildroot.net/results/14c/14cf165e63fd7bb076d7c8f5aab92d24aa4622c4/



Patch status: sent upstream.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>