removed redundant wchar_t declaration

Author: ZERICO2005

src/libc/include/stddef.h

@@ -7,13 +7,6 @@
 
 typedef __PTRDIFF_TYPE__ ptrdiff_t;
 
-#ifndef _WCHAR_T_DEFINED
-#define _WCHAR_T_DEFINED
-#ifndef __cplusplus
-typedef __WCHAR_TYPE__ wchar_t;
-#endif /* __cplusplus */
-#endif /* _WCHAR_T_DEFINED */
-
 #if __STDC_VERSION__ >= 199901L || __cplusplus >= 201103L
 typedef struct {
     long long    __max_align_ll __attribute__((__aligned__(__alignof__(  long long))));