Fix dwarf_reader.cc for C++11

This commit replaces `std::make_pair<int, std::string>(dirindex, path)`
with `std::make_pair(dirindex, path)` because C++11 replaces
`std::make_pair<T, V>(T t, V v)` with
`std::make_pair<T, V>(T &&t, V &&v)`.

This commit removes explicit template arguments because forward
references are only available during template arguments deduction.  If
the explicit template arguments are specified, the argument `t` and `v`
will become R-value references, which can not bind to an L-value.

Test: It builds with clang++ (or g++) with CXXFLAGS="-std=c++11"
Change-Id: I79eb94552445354f7e7bff02169879195c7f6283
diff --git a/binutils-2.27/gold/dwarf_reader.cc b/binutils-2.27/gold/dwarf_reader.cc
index 6c2b008..c750ae4 100644
--- a/binutils-2.27/gold/dwarf_reader.cc
+++ b/binutils-2.27/gold/dwarf_reader.cc
@@ -1961,7 +1961,7 @@
 	}
       gold_debug(DEBUG_LOCATION, "File %3d: %s",
 		 static_cast<int>(file_list.size()), path);
-      file_list.push_back(std::make_pair<int, std::string>(dirindex, path));
+      file_list.push_back(std::make_pair(dirindex, path));
     }
 
   delete[] types;