+/* ticks left before next pre-emptive context switch */
+int ticks_to_ctxt_switch = 0;
+
+static
+void
+#if defined(mingw32_TARGET_OS) || (defined(cygwin32_TARGET_OS) && !defined(HAVE_SETITIMER))
+CALLBACK
+handle_tick(UINT uID STG_UNUSED, UINT uMsg STG_UNUSED, DWORD dwUser STG_UNUSED,
+ DWORD dw1 STG_UNUSED, DWORD d STG_UNUSED);
+#else
+handle_tick(int unused STG_UNUSED);
+#endif