gdi32: Implement MirrorRgn.
diff --git a/include/wingdi.h b/include/wingdi.h
index fa68c23..e10bbe9 100644
--- a/include/wingdi.h
+++ b/include/wingdi.h
@@ -3601,6 +3601,7 @@
 WINGDIAPI BOOL        WINAPI LineTo(HDC,INT,INT);
 WINGDIAPI BOOL        WINAPI LPtoDP(HDC,LPPOINT,INT);
 WINGDIAPI BOOL        WINAPI MaskBlt(HDC,INT,INT,INT,INT,HDC,INT,INT,HBITMAP,INT,INT,DWORD);
+WINGDIAPI BOOL        WINAPI MirrorRgn(HWND,HRGN);
 WINGDIAPI BOOL        WINAPI ModifyWorldTransform(HDC,const XFORM *, DWORD);
 WINGDIAPI BOOL        WINAPI MoveToEx(HDC,INT,INT,LPPOINT);
 WINGDIAPI INT         WINAPI OffsetClipRgn(HDC,INT,INT);