SDL_iconv.c (encodings): mark "WCHAR_T" as ENCODING_UTF16LE for OS/2 too

whcar_t is unsigned short in os/2, like windows

src/stdlib/SDL_iconv.c

@@ -146,7 +146,7 @@ static struct
     { "US-ASCII", ENCODING_ASCII },
     { "8859-1", ENCODING_LATIN1 },
     { "ISO-8859-1", ENCODING_LATIN1 },
-#ifdef __WIN32__
+#if defined(__WIN32__)||defined(__OS2__)
     { "WCHAR_T", ENCODING_UTF16LE },
 #else
     { "WCHAR_T", ENCODING_UCS4NATIVE },