Fixing build problems due to endian.h

Have to define _DEFAULT_SOURCE before you can use the endian
conversion functions.  As most standard library headers use
features.h, and _DEFAULT_SOURCE must be defined before features.h is
included, we have to include base.h before other headers.

lib/base.h

@@ -13,6 +13,8 @@
 #ifndef BASE_H
 #define BASE_H
 
+#define _DEFAULT_SOURCE
+#include <endian.h>
 #include <stdint.h>
 
 /* Basic macros for a variety of uses.  Quite self explanatory. */