some tty updates

Add a note about NO_TERMS to include/wintty.h for clarity.

Rename tty_startup and tty_shutdown to term_startup() and
term_shutdown(). They are found in termcap.c for !NO_TERMS
like most of the other term_ routines, as well as having
versions for several of the NO_TERMS platforms. They aren't
part of the tty_interface called from the core. The tty
implementation does call and rely on them.

Remove some conditional #ifdef's around term_shutdown()
(formerly tty_shutdown()) and just ensure that all the
tty platforms have an implementation that they can link
with, even if it is just a stub presently.

Put the protype for nethack_exit in extern.h to reduce
maintenance to a single spot, and remove it from other
locations. A warning in the msdos cross-compile led to
this change.

include/extern.h

@@ -2098,6 +2098,7 @@ extern void consoletty_open(int);
 extern void consoletty_rubout(void);
 extern int tgetch(void);
 extern int console_poskey(coordxy *, coordxy *, int *);
+void console_g_putch(int in_ch);
 extern void set_output_mode(int);
 extern void synch_cursor(void);
 extern void nethack_enter_consoletty(void);
@@ -2302,7 +2303,14 @@ extern int getlock(void);
 extern const char *get_portable_device(void);
 #endif
 
-/* ### pcsys.c ### */
+/* ### pcsys.c, windsys.c ### */
+#if defined(MICRO) || defined(WIN32)
+ATTRNORETURN extern void nethack_exit(int) NORETURN;
+#else
+#define nethack_exit exit
+#endif
+
+/* ### pcsys.c  ### */
 
 #if defined(MICRO) || defined(WIN32)
 extern void flushout(void);