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/tc7.0.x/trunk@1590838 13f79535-47bb-0310-9956-ffa450edef68