win,tty: remove deadcode

Not used anywhere or exported. Most of this code also cares which
direction handle is open too (Input or Output), so it's not particularly
useful.

PR-URL: #1964
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

src/win/tty.c

@@ -382,12 +382,6 @@ int uv_tty_set_mode(uv_tty_t* tty, uv_tty_mode_t mode) {
 }
 
 
-int uv_is_tty(uv_file file) {
-  DWORD result;
-  return GetConsoleMode((HANDLE) _get_osfhandle(file), &result) != 0;
-}
-
-
 int uv_tty_get_winsize(uv_tty_t* tty, int* width, int* height) {
   CONSOLE_SCREEN_BUFFER_INFO info;