Made $[%name] to retrieve keyword values in a tag. Has bugs.

__header.cpp

@@ -21,7 +21,7 @@ namespace jet {
       if(keywordDefined("expr")) {
 	 if(keywordDefined("eval"))
 	   throw coreutils::Exception("Cannot use eval with expr.");	 
-	 global.headers[keywords["name"]] = Operand(keywords["expr"], global, parent->variables).string;	    
+	 global.headers[keywords["name"]] = Operand(keywords["expr"], global, parent->variables, keywords).string;	    
       } else if(hasContainer) {
 	 processContainer(container);
 	 if(evaluate) {