Version-incompatible code now moved to HadoopShim subclasses.
HadoopShim singleton instance dynamically loaded based on VersionInfo.
Separate MRUnit builds from Apache and CDH placed in /lib subdirs.
Modified 'ant package' target to properly include all shims.
From: Aaron Kimball <aaron@cloudera.com>
git-svn-id: https://svn.apache.org/repos/asf/incubator/sqoop/trunk@1149880 13f79535-47bb-0310-9956-ffa450edef68
