Move test for genrb from the icu_prefix determination into the icu msgloader test, since genrb is used only by the icu msgloader.
It's nice to know that Alberto is watching my back.


git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@408982 13f79535-47bb-0310-9956-ffa450edef68