Curses: partial stack unselecting

In curses, selecting a partial stack, then unselecting the entry,
and then selecting it normally, the entry still kept the quantity
from the partial selection. Make it behave like all the other
windowports by resetting the quantity when the entry is unselected.

doc/fixes3-7-0.txt

@@ -1636,6 +1636,8 @@ curses: ensure alt+'A' through alt+'Z' and alt+'a' through alt+'z' work
 	correctly with PDCURSES
 curses: fix an off-by-one error when deciding whether a long line on the
 	bottom line of the message window can fit ">>" (curses' "--More--")
+curses: selecting a partial stack, unselecting it, and then selecting it
+	normally did not reset the quantity to the whole stack
 macOS: Xcode project was failing to build if the path to the NetHack source
 	tree contained a space; the issue was within some shell script code
 	contained within the project

win/curses/cursdial.c

@@ -1636,6 +1636,7 @@ menu_select_deselect(
 
     if (operation == DESELECT || (item->selected && operation == INVERT)) {
         item->selected = FALSE;
+        item->count = -1L;
         if (visible) {
             mvwaddch(win, item->line_num + 1, 1, ' ');
             curses_toggle_color_attr(win, HIGHLIGHT_COLOR, NONE, ON);