Fix https://issues.apache.org/bugzilla/show_bug.cgi?id=54338
Correctly coerce the value to the expected type when using the tag plug-in for the JSTL set tag. Patch provided by Sheldon Shao.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1429156 13f79535-47bb-0310-9956-ffa450edef68