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.c

@@ -10,11 +10,10 @@
  * Description: Implementation of basic library functions
  */
 
-#include <endian.h>
-#include <string.h>
-
 #include "./base.h"
 
+#include <string.h>
+
 hword convert_bytes_to_hword(byte *bytes)
 {
   hword be_h = 0;

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. */

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)

lib/inst.h

@@ -13,12 +13,12 @@
 #ifndef INST_H
 #define INST_H
 
-#include <stdio.h>
-#include <stdlib.h>
-
 #include <lib/base.h>
 #include <lib/darr.h>
 
+#include <stdio.h>
+#include <stdlib.h>
+
 typedef enum
 {
   OP_NOOP = 0,