Do not import system headers into namespace std.
Fixes "error: reference to 'std' is ambiguous".
--- src/expr.cpp.orig	2002-10-20 08:03:12.000000000 -0500
+++ src/expr.cpp	2018-10-08 00:38:51.000000000 -0500
@@ -14,14 +14,11 @@
 
 #line 1 "expr.y"
 
-namespace std {  
 #include <stdio.h>
 #include <memory.h>
 #include <stdlib.h>
 #include <string.h>
-}
 
-using namespace std;
  
 #include "System.h"
 #include "elf.h"