Stop using malloc.h in favor of stdlib.h; should actually introduce _OU_TARGET_OS_OPENBSD

--- ou/src/ou/malloc.cpp.orig	Wed Jan 13 23:09:57 2016
+++ ou/src/ou/malloc.cpp	Wed Jan 13 23:11:34 2016
@@ -29,7 +29,8 @@
 #include <ou/customization.h>
 #include <ou/macros.h>
 
-#if _OU_TARGET_OS == _OU_TARGET_OS_MAC || _OU_TARGET_OS == _OU_TARGET_OS_IOS
+#if _OU_TARGET_OS == _OU_TARGET_OS_MAC || _OU_TARGET_OS == _OU_TARGET_OS_IOS \
+	|| defined(__OpenBSD__)
 
 #include <stdlib.h>