postgresql: add host-zic dependency

Fixes zic related build failure [1], patch suggested by
Yann E. MORIN [2].

[1] http://autobuild.buildroot.net/results/9ec69f92a48c1adc50bdb3096008243d842c27e6/
[2] http://lists.busybox.net/pipermail/buildroot/2014-April/094767.html



Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>