Correct the handling of back-slash escaping in the EL parser and no longer
require that "\$" or "\#" must be followed by "{" in order for the back-slash
escaping to take effect.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1593836 13f79535-47bb-0310-9956-ffa450edef68