Work on if, call and system tags.

__call.cpp

@@ -1,4 +1,4 @@
-#include "__call.h"
+#include "__system.h"
 #include "Exception.h"
 #include "MString.h"
 #include <stdlib.h>
@@ -8,7 +8,7 @@
 
 namespace jet {
    
-   __call::__call(coreutils::ZString &in, coreutils::MString &out, Global &global) : Tag(in, out, global) {
+   __system::__system(coreutils::ZString &in, coreutils::MString &out, Global &global) : Tag(in, out, global) {
       if(hasContainer)
 	throw coreutils::Exception("call cannot have a container.");	
       if(!variableDefined(coreutils::ZString("pgm")))