netbsd: Support curses libraries without ncurses mouse support

This adds a configure check for the ncurses getmouse() function
and disables mouse-related code paths when mouse support is
not present in the curses library.

This is necessary for stable versions of NetBSD's libcurses, the
development version has stub mouse functions for compatibility
with ncurses.

Signed-off-by: Nia Alarie <nia@NetBSD.org>

InfoScreen.c

@@ -106,6 +106,7 @@ void InfoScreen_run(InfoScreen* this) {
          }
       }
 
+#ifdef HAVE_GETMOUSE
       if (ch == KEY_MOUSE) {
          MEVENT mevent;
          int ok = getmouse(&mevent);
@@ -127,6 +128,7 @@ void InfoScreen_run(InfoScreen* this) {
             #endif
          }
       }
+#endif
 
       if (this->inc->active) {
          IncSet_handleKey(this->inc, ch, panel, IncSet_getListItemValue, this->lines);