Fix to use configured openpty usability condition

No reason to restrict only on OpenBSD and FreeBSD here.

Signed-off-by: OBATA Akio <obache@wizdas.com>
(cherry picked from commit 12364c9cc3)

tdecore/kpty.cpp

@@ -308,7 +308,7 @@ bool KPty::open()
   if (d->masterFd >= 0)
     return true;
 
-#if defined(__OpenBSD__) || defined(__FreeBSD__)
+#if defined(HAVE_OPENPTY)
   char cpty[16];
 
   if (openpty(&d->masterFd, &d->slaveFd, cpty, NULL, &d->winSize) == 0) {