The build script (used only on MSVC, not MingW or other OSes) for icu
generates nmake makefiles for the build using icu's
source/allinone/allinone.sln, in which layoutex doesn't list a dependency
on i18n, despite linking to icuin.lib from i18n, which sporadically causes
the icu build to fail. This is really an upstream bug, however upstream
doesn't build using allinone.sln so we are affected more.

This patch declares the missing dependecy, and makes icu build reliably.

Patch by: me
Tested by: pats