ICU-7287 Forgot to force the plug-in version number in tagged version.  Just adding the property for specifying the version.

X-SVN-Rev: 27256
diff --git a/build.properties b/build.properties
index 3f6d5fb..3934270 100644
--- a/build.properties
+++ b/build.properties
@@ -27,4 +27,6 @@
 default.target.rt.version=JAVASE6
 
 icu4j.plugin.impl.version.string=4.2.1
-copyright.eclipse=Licensed Materials - Property of IBM \n (C) Copyright IBM Corp. 2000, 2010. All Rights Reserved. \n IBM is a registered trademark of IBM Corp.
\ No newline at end of file
+copyright.eclipse=Licensed Materials - Property of IBM \n (C) Copyright IBM Corp. 2000, 2010. All Rights Reserved. \n IBM is a registered trademark of IBM Corp.
+
+icu4j.eclipse.build.version.string=4.2.1.v20100112