Fix compilation issues on OS X - mainly #include file changes (Lars Immisch)

diff --git a/tests/db/db_test.c b/tests/db/db_test.c
index 93bf152..bbca585 100644
--- a/tests/db/db_test.c
+++ b/tests/db/db_test.c
@@ -22,7 +22,7 @@
 
 #include <stdio.h>
 #include <string.h>
-#include <malloc.h>
+#include <stdlib.h>
 
 #define COMPARE(original, copy) \
 	if (original->id != copy->id) \