Move code that parses EL expressions within JSP template text from Parser to JspReader class.
This is done to get access to JspReader.nextChar(mark) to avoid calling reader.mark() in a loop, as that method allocates new Mark object on each call.

Also removed duplicate "start = reader.mark();" call, as parseELExpression() does update 'start'.
It is backport of r1601924.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1601934 13f79535-47bb-0310-9956-ffa450edef68