Fix T71273: Bad encoding of utf-8 for Text objects

`BLI_strncpy_wchar_from_utf8` internally assumes `wchar_t` is 32 bits
which is not the case on windows.

The solution is to replace `wchar_t` with `char32_t`.

Thanks to @robbott for compatibility on macOS.

Differential Revision: https://developer.blender.org/D6198

source/blender/blenkernel/intern/object_dupli.c

@@ -491,7 +491,7 @@ static void make_duplis_font(const DupliContext *ctx)
   float vec[3], obmat[4][4], pmat[4][4], fsize, xof, yof;
   int text_len, a;
   size_t family_len;
-  const wchar_t *text = NULL;
+  const char32_t *text = NULL;
   bool text_free = false;
 
   /* font dupliverts not supported inside collections */