patch 8.1.1081: MS-Windows: cannot use some fonts

Problem:    MS-Windows: cannot use fonts whose name cannot be represented in
            the current code page.
Solution:   Use wide font functions. (Ken Takata, closes #4000)
diff --git a/src/proto/gui_w32.pro b/src/proto/gui_w32.pro
index 75edd4b..9f2e5fb 100644
--- a/src/proto/gui_w32.pro
+++ b/src/proto/gui_w32.pro
@@ -70,7 +70,7 @@
 void gui_mch_set_fg_color(guicolor_T color);
 void gui_mch_set_bg_color(guicolor_T color);
 void gui_mch_set_sp_color(guicolor_T color);
-void im_set_font(LOGFONT *lf);
+void im_set_font(LOGFONTW *lf);
 void im_set_position(int row, int col);
 void im_set_active(int active);
 int im_get_status(void);