Fix the JSP Remote File Inclusion (RFI) example

[postmodern]

For some reason we cannot include the webapp/include.jsp file into webapp/rfi.jsp.

Type Exception Report

Message The absolute uri: [http://java.sun.com/jsp/jstl/core] cannot be resolved in either web.xml or the jar files deployed with this application

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

org.apache.jasper.JasperException: The absolute uri: [http://java.sun.com/jsp/jstl/core] cannot be resolved in either web.xml or the jar files deployed with this application
	org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:55)
	org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:294)
	org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:81)
	org.apache.jasper.compiler.TagLibraryInfoImpl.generateTldResourcePath(TagLibraryInfoImpl.java:251)
	org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:122)
	org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:431)
	org.apache.jasper.compiler.Parser.parseDirective(Parser.java:489)
	org.apache.jasper.compiler.Parser.parseElements(Parser.java:1445)
	org.apache.jasper.compiler.Parser.parse(Parser.java:144)
	org.apache.jasper.compiler.ParserController.doParse(ParserController.java:244)
	org.apache.jasper.compiler.ParserController.parse(ParserController.java:105)
	org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:206)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:384)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:361)
	org.apache.jasper.compiler.Compiler.compile(Compiler.java:345)
	org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:603)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)