Remove all uses of 'using std::error_code' from headers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210866 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-readobj/llvm-readobj.h

@@ -14,13 +14,12 @@
 #include <string>
 
 namespace llvm {
-using std::error_code;
   namespace object {
     class RelocationRef;
   }
 
   // Various helper functions.
-  bool error(error_code ec);
+  bool error(std::error_code ec);
   bool relocAddressLess(object::RelocationRef A,
                         object::RelocationRef B);
 } // namespace llvm