[UCRT] Import Microsoft.Windows.SDK.CRTSource version 10.0.22621.3

Imported from https://www.nuget.org/packages/Microsoft.Windows.SDK.CRTSource/10.0.22621.3
License: MIT

sdk/lib/ucrt/string/wcsncnt.cpp

@@ -0,0 +1,24 @@
+//
+// wcsncnt.cpp
+//
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+//
+// Defines __wcsncnt(), which returns the number of characters in a string.  If
+// the string is longer than the given 'count', 'count' is returned.
+//
+#include <string.h>
+
+
+
+extern "C" size_t __cdecl __wcsncnt(
+    wchar_t const* const string,
+    size_t         const count
+    )
+{
+    wchar_t const* it = string;
+    size_t n = 0;
+
+    for (; *it && n != count; ++it, ++n) { }
+
+    return n;
+}