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/objclosure.c b/py/objclosure.c
index 7f6bcf4..0f4816e 100644
--- a/py/objclosure.c
+++ b/py/objclosure.c
@@ -6,6 +6,7 @@
 #include "nlr.h"
 #include "misc.h"
 #include "mpconfig.h"
+#include "qstr.h"
 #include "obj.h"
 #include "runtime.h"