sysdeps: Stop pretending _dbus_set_signal_handler is portable to Windows

None of the things we rely on in POSIX async signal handlers, such
as the existence of async-signal-safe write(), are portable to Windows,
so the async signal handlers that use this function are #ifdef
DBUS_UNIX anyway. Remove the unused stub function from the
Windows side, and move the declaration to the Unix-specific header.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=103010
Signed-off-by: Simon McVittie <smcv@collabora.com>
Reviewed-by: Philip Withnall <withnall@endlessm.com>

dbus/dbus-sysdeps-unix.h

@@ -165,6 +165,12 @@ DBUS_PRIVATE_EXPORT
 dbus_bool_t _dbus_ensure_standard_fds (DBusEnsureStandardFdsFlags   flags,
                                        const char                 **error_str_p);
 
+/** A UNIX signal handler */
+typedef void (* DBusSignalHandler) (int sig);
+
+void _dbus_set_signal_handler (int               sig,
+                               DBusSignalHandler handler);
+
 /** @} */
 
 DBUS_END_DECLS

dbus/dbus-sysdeps-util-win.c

@@ -296,18 +296,6 @@ _dbus_rlimit_free (DBusRLimit *lim)
   _dbus_assert (lim == NULL);
 }
 
-/** Installs a signal handler
- *
- * @param sig the signal to handle
- * @param handler the handler
- */
-void
-_dbus_set_signal_handler (int               sig,
-                          DBusSignalHandler handler)
-{
-  _dbus_verbose ("has to be implemented\n");
-}
-
 /**
  * stat() wrapper.
  *

dbus/dbus-sysdeps.h

@@ -541,12 +541,6 @@ dbus_bool_t _dbus_command_for_pid (unsigned long  pid,
                                    int            max_len,
                                    DBusError     *error);
 
-/** A UNIX signal handler */
-typedef void (* DBusSignalHandler) (int sig);
-
-void _dbus_set_signal_handler (int               sig,
-                               DBusSignalHandler handler);
-
 dbus_bool_t _dbus_user_at_console (const char *username,
                                    DBusError  *error);