move u8char position

inc/hgl/platform/compiler/Microsoft.h

@@ -18,6 +18,12 @@
 
 #define HGL_THREAD_LOCAL_STORAGE        __declspec(thread)                              //线程本地储存
 //--------------------------------------------------------------------------------------------------
+#if _MSVC_LANG>=201704L         //C++20
+using u8char    =char8_t;
+#else
+using u8char    =char;
+#endif
+
 #define HGL_FMT_I64            "%I64d"
 #define HGL_FMT_U64            "%I64u"
 //参考文档最后查阅支持版本为VC2013，网址：http://msdn.microsoft.com/en-us/library/tcxf1dw6.aspx

inc/hgl/platform/os/MSWindows.h

@@ -11,7 +11,6 @@
 //--------------------------------------------------------------------------------------------------
 using u32char           =char32_t;
 using u16char           =wchar_t;
-using u8char            =char8_t;
 using os_char           =wchar_t;
 
 #define to_oschar       to_u16