[atomix] Fix compilation with gcc10 / -fno-common

[Robert Roth <robertroth src gnome org>]

commit be7f44f1945a569494d46c60eaf6e7b39b2bb48b
Author: Hans de Goede <hdegoede redhat com>
Date:   Tue Feb 25 10:15:42 2020 +0100

    Fix compilation with gcc10 / -fno-common
    
    gcc10 defaults to -fno-common, meaning that non static symbols can
    only be declared once. Make the parent_class variable in level.c and
    theme.c static to fix building with gcc10.

 src/level.c | 2 +-
 src/theme.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/level.c b/src/level.c
index 160672d..5fbf6af 100644
--- a/src/level.c
+++ b/src/level.c
@@ -31,7 +31,7 @@ static void level_class_init (GObjectClass *class);
 static void level_init (Level *level);
 static void level_finalize (GObject *object);
 
-GObjectClass *parent_class;
+static GObjectClass *parent_class;
 
 /*=================================================================
  
diff --git a/src/theme.c b/src/theme.c
index 45f3086..88acb00 100644
--- a/src/theme.c
+++ b/src/theme.c
@@ -32,7 +32,7 @@ static void theme_init (Theme *theme);
 static void theme_finalize (GObject *object);
 static void destroy_theme_image (gpointer data);
 
-GObjectClass *parent_class;
+static GObjectClass *parent_class;
 
 GType theme_get_type (void)
 {