apply suggested changes

Author: farmerpiki

source/cppfront.cpp

@@ -72,7 +72,7 @@ auto main(
             }
             else {
                 std::cerr << arg.text << " - ambiguous compiler flag name, did you mean one of these?\n";
-                for (auto const &a : ambiguous) {
+                for (auto const& a : ambiguous) {
                     std::cerr << "    " << arg.text.front() << a << "\n";
                 }
             }

source/to_cpp1.h

@@ -617,7 +617,7 @@ class positional_printer
     //
     auto open(
         std::string const&          cpp2_filename_,
-        std::string                 cpp1_filename_,
+        std::string const&          cpp1_filename_,
         std::vector<comment> const& comments,
         cpp2::source const&         source,
         cpp2::parser const&         parser
@@ -632,7 +632,7 @@ class positional_printer
             && !pcomments
             && "ICE: tried to call .open twice"
         );
-        cpp1_filename = std::move(cpp1_filename_);
+        cpp1_filename = cpp1_filename_;
         if (cpp1_filename == "stdout") {
             out = &std::cout;
         }