Some work on call tag.

__system.cpp

@@ -10,7 +10,7 @@ namespace jet {
    
    __system::__system(coreutils::ZString &in, coreutils::MString &out, Global &global) : Tag(in, out, global) {
       if(hasContainer)
-	throw coreutils::Exception("call cannot have a container.");	
+	throw coreutils::Exception("system tag cannot have a container.");	
       if(!variableDefined(coreutils::ZString("pgm")))
 	throw coreutils::Exception("pgm keyword must be specified.");
       argv[0] = variables["pgm"].c_str(); // TODO: Need to peel off the program name only and pass as argv[0].