Avoid conflicting efi_char16_t type definitions

It's not necessary to define 'efi_char16_t' as 'wchar_t' since we don't
need any wchar functions. Besides, it may conflict with efivar-38. This
commit defines 'efi_char16_t' as 'uint16_t' and adds the conditional
check to avoid the potential conflict.

Fixes: #66

Signed-off-by: Gary Lin <glin@suse.com>

src/mokutil.h

@@ -33,13 +33,14 @@
 #define __MOKUTIL_H__
 
 #include <ctype.h>
-#include <wchar.h>
 
 #include "signature.h"
 
 typedef unsigned long efi_status_t;
 typedef uint8_t efi_bool_t;
-typedef wchar_t efi_char16_t;		/* UNICODE character */
+#ifndef efi_char16_t
+typedef uint16_t efi_char16_t;		/* UNICODE character */
+#endif
 
 typedef enum {
 	DELETE_MOK = 0,