custompline(SUPPRESS_HISTORY,...) for curses

The curses interface already has a hack to keep 'Count: 12', 'Count:
123' intermediate multi-digit counts out of its message recall history
for ^P, but it was flushing real messages when getpos()'s 'autodescribe'
reported what the cursor moved over.  Overload the count hack to support
 putstr(WIN_MESSAGE, ATR_NOHISTORY, text)
(which is what custompline(SUPPRESS_HISTORY, ...) eventually calls).

The conditional logic for when to create the 'count_window' was pretty
convoluted.  This simplification has the same semantics but I don't
have PDCURSES to actually verify that.

win/curses/cursmisc.c

@@ -632,7 +632,7 @@ curses_get_count(int first_digit)
             current_count = LARGEST_INT;
         }
 
-        pline("Count: %ld", current_count);
+        custompline(SUPPRESS_HISTORY, "Count: %ld", current_count);
         current_char = curses_read_char();
     }
 
@@ -647,13 +647,17 @@ curses_get_count(int first_digit)
 
 
 /* Convert the given NetHack text attributes into the format curses
-understands, and return that format mask. */
+   understands, and return that format mask. */
 
 int
 curses_convert_attr(int attr)
 {
     int curses_attr;
 
+    /* first, strip off control flags masked onto the display attributes
+       (caller should have already done this...) */
+    attr &= ~(ATR_URGENT | ATR_NOHISTORY);
+
     switch (attr) {
     case ATR_NONE:
         curses_attr = A_NORMAL;