crt: Update the decoration of the EditWndProc symbol to EditWndProc@20

This function seems to be undocumented (we don't have any declaration
of it in any header), but this is the form it gets dumped from current
user32.dll.

Signed-off-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Jonathan Yong <10walls@gmail.com>
diff --git a/mingw-w64-crt/lib32/user32.def b/mingw-w64-crt/lib32/user32.def
index 56207f3..ac3164d 100644
--- a/mingw-w64-crt/lib32/user32.def
+++ b/mingw-w64-crt/lib32/user32.def
@@ -247,7 +247,7 @@
 DwmStartRedirection@8 ; Mentioned on http://habrahabr.ru/post/145174/ , enables GDI virtualization (for security purposes)
 DwmStopRedirection@0
 DwmValidateWindow@8
-EditWndProc@16
+EditWndProc@20
 EmptyClipboard@0
 EnableMenuItem@12
 EnableMouseInPointer@4