Fix up std:: namespace hygiene.

* Remove all uses of `using namespace std` from header files (although a
  few specific cases of things like `using std::vector` remain)
* Move all existing uses of `using namespace std` in cpp files to after the
  header includes
* Make coordinating changes so it builds again.

Qt6 builds on Windows were breaking because of namespace collision between
std::byte and some version of `byte` in one of Qt's namespaces.  That breakage
is now fixed.

It would be good to systematically clean up all `using` declarations in header
files to ensure nothing is leaking out, but that's for another time.

1 files changed, 1 insertions, 2 deletions

diff --git a/enumerator.h b/enumerator.h
index 5d2c2d9..eddef1f 100644
--- a/enumerator.h
+++ b/enumerator.h
@@ -20,11 +20,10 @@
 #define QUACKLE_ENUMERATOR_H
 
 #include <vector>
+using std::vector;
 
 #include "bag.h"
 
-using namespace std;
-
 namespace Quackle
 {
 class Bag;