articles: ctod: change wchar_t to druntime headers equivalents

Co-authored-by: Petar Kirov <petar.p.kirov@gmail.com>
Signed-off-by: Luís Ferreira <contact@lsferreira.net>

Author: ljmf00

articles/ctod.dd

@@ -85,7 +85,7 @@ signed char        =>        byte
 unsigned char      =>        ubyte
 short              =>        short
 unsigned short     =>        ushort
-wchar_t            =>        wchar
+wchar_t            =>        core.stdc.stddef.wchar_t
 int                =>        int
 unsigned           =>        uint
 long               =>        core.stdc.config.c_long