curses perm_invent tweak

If there's room, avoid writing the column indicator (when one or more
entries have been truncated due to insufficient window width) on an
entry.  Only applies to first page so only matters if sortpack is off.

Also, for windowborders=3 or 4, where the map, message, and status
windows have borders but the perm_invent one doesn't, insert a blank
line at the top when there is only one line of output (such as "not
carrying anything") so that it lines up with the top line inside the
adjacent window rather than with that window's top border.  No effect
when perm_invent itself has a border or when none of the others do.

win/curses/cursmain.c

@@ -689,10 +689,11 @@ curses_add_menu(winid wid, const glyph_info *glyphinfo,
     attr &= ~(ATR_URGENT | ATR_NOHISTORY);
     curses_attr = curses_convert_attr(attr);
 
+    /* 'inv_update': 0 for normal menus, 1 and up for perminv window */
     if (inv_update) {
         /* persistent inventory window; nothing is selectable;
            omit glyphinfo because perm_invent is to the side of
-           the map so usually cramped for space */
+           the map so usually cramped for horizontal space */
         curs_add_invt(inv_update, accelerator, curses_attr, str);
         inv_update++;
         return;