Resolve DEBUG compilation issues

Use NDEBUG conditional instead of DEBUG.

Do not call static functions in extern inline ones.
    Vector.c:67:11: error: static function 'Vector_isConsistent' is used in an inline function with external linkage [-Werror,-Wstatic-in-inline]

1 files changed, 2 insertions, 2 deletions

diff --git a/Hashtable.h b/Hashtable.h
index 144f01cf..aacbb340 100644
--- a/Hashtable.h
+++ b/Hashtable.h
@@ -26,11 +26,11 @@ struct Hashtable_ {
    bool owner;
 };
 
-#ifdef DEBUG
+#ifndef NDEBUG
 
 int Hashtable_count(Hashtable* this);
 
-#endif
+#endif /* NDEBUG */
 
 Hashtable* Hashtable_new(int size, bool owner);