Fix autotools on FreeBSD.

Endianness fun is not provided by the same header file on GNU/Linux (endian.h) and FreeBSD (sys/endian.h).  Add some magic for the autotools to detect the correct header file.  While here, add AC_C_INLINE: it's reported as missing by autoscan(1).

mifare_classic.c

@@ -29,8 +29,16 @@
  * October 6, 2008
  */
 
-#define _BSD_SOURCE
-#include <endian.h>
+#include "config.h"
+
+#if defined(HAVE_SYS_ENDIAN_H)
+#  include <sys/endian.h>
+#endif
+
+#if defined(HAVE_ENDIAN_H)
+#  define _BSD_SOURCE
+#  include <endian.h>
+#endif
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>