patch 9.0.0058: Win32: cannot test low level events

Problem:    Win32: cannot test low level events.
Solution:   Add "sendevent" to test_gui_event(). (Yegappan Lakshmanan,
            closes #10679)
diff --git a/src/proto/gui_w32.pro b/src/proto/gui_w32.pro
index 43484ad..cab3343 100644
--- a/src/proto/gui_w32.pro
+++ b/src/proto/gui_w32.pro
@@ -96,4 +96,5 @@
 BalloonEval *gui_mch_create_beval_area(void *target, char_u *mesg, void (*mesgCB)(BalloonEval *, int), void *clientData);
 void gui_mch_destroy_beval_area(BalloonEval *beval);
 void netbeans_draw_multisign_indicator(int row);
+int test_gui_w32_sendevent(dict_T *args);
 /* vim: set ft=c : */