With mpd's build system, it requires either an iconv built into the libc
or icu. Since uClibc-ng as configured by OpenWrt currently has no iconv,
use icu for it to work around the problem. This is the simplest solution.

Added a patch to use boost's rounding functions. They are more appropriate
and work with uClibc-ng.

Signed-off-by: Rosen Penev <rosenp@gmail.com>