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/inst.c

@@ -10,13 +10,13 @@
  * Description: Implementation of bytecode for instructions
  */
 
+#include "./inst.h"
+
 #include <assert.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 
-#include "./inst.h"
-
 const char *opcode_as_cstr(opcode_t code)
 {
   switch (code)