Revamp qstrs: they now include length and hash.

Can now have null bytes in strings.  Can define ROM qstrs per port using
qstrdefsport.h
diff --git a/py/map.c b/py/map.c
index 1ce763a..9f919e0 100644
--- a/py/map.c
+++ b/py/map.c
@@ -4,6 +4,7 @@
 
 #include "misc.h"
 #include "mpconfig.h"
+#include "qstr.h"
 #include "obj.h"
 #include "runtime0.h"
 #include "map.h"