upgrade to icu 54

Change-Id: I4d32ac386ff8b69bee4319e673769917045d9450
Reviewed-on: https://gerrit.libreoffice.org/13547
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>