[gtk: 1/2] Add a missing extern, to fix building with -fno-common

[Matthias Clasen <matthiasc src gnome org>]

commit 25a53276e0ca402113351b73e5f0d44cb9a90ff6
Author: Martin Storsjö <martin martin st>
Date:   Sun Apr 5 00:43:16 2020 +0300

    Add a missing extern, to fix building with -fno-common
    
    With C compilers defaulting to -fcommon, this isn't an issue, but
    upcoming compilers (GCC 10 and Clang 11) will default to -fno-common,
    ending up with duplicate definitions of these variables.

 gdk/win32/gdkprivate-win32.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gdk/win32/gdkprivate-win32.h b/gdk/win32/gdkprivate-win32.h
index f0c651e11f..ea86a917a3 100644
--- a/gdk/win32/gdkprivate-win32.h
+++ b/gdk/win32/gdkprivate-win32.h
@@ -288,10 +288,10 @@ extern UINT              _gdk_input_codepage;
 extern guint             _gdk_keymap_serial;
 
 /* The singleton clipdrop object pointer */
-GdkWin32Clipdrop *_win32_clipdrop;
+extern GdkWin32Clipdrop *_win32_clipdrop;
 
 /* Used to identify the main thread */
-GThread          *_win32_main_thread;
+extern GThread          *_win32_main_thread;
 
 void _gdk_win32_dnd_do_dragdrop (void);