Temporary disable code which references mch_resolve_shortcut

This function is only used for windows
'mch_resolve_shortcut' can be found in vim source src/os_mswin.c
-> mch_resolve_shortcut(char_u *fname)

Spotted by @equalsraf, see PR neovim#2609

src/nvim/buffer.c

@@ -3995,7 +3995,9 @@ void fname_expand(buf_T *buf, char_u **ffname, char_u **sfname)
     *sfname = *ffname;
   *ffname = (char_u *)fix_fname((char *)*ffname);     /* expand to full path */
 
-#ifdef WIN32
+// TODO(Hettomei,equalsraf): Temporary disable this block
+// because mch_resolve_shortcut has gone from source tree.
+#if 0
   if (!buf->b_p_bin) {
     char_u  *rfname;
 

src/nvim/eval.c

@@ -13438,7 +13438,9 @@ static void f_resolve(typval_T *argvars, typval_T *rettv)
 #endif
 
   p = get_tv_string(&argvars[0]);
-#ifdef WIN32
+#if 0
+// TODO(Hettomei,equalsraf): Temporary disable this block
+// because mch_resolve_shortcut has gone from source tree.
   {
     char_u  *v = NULL;