gtk/tests: Fix for -Wmissing-declarations

I'm adding a bunch of fixes for gcc complaining about
-Wmissing-declarations after finding a bunch of cases today where I
had forgotten to make functions static in the CSS code.

This patch fixes the tests in gtk/tests.

After this last patch, the gtk/ subdir should now compile without
warnings when this flag is enabled.

gtk/tests/builder.c

@@ -25,6 +25,16 @@
 #include <gtk/gtk.h>
 #include <gdk/gdkkeysyms.h>
 
+/* exported for GtkBuilder */
+void signal_normal (GtkWindow *window, GParamSpec spec);
+void signal_after (GtkWindow *window, GParamSpec spec);
+void signal_object (GtkButton *button, GParamSpec spec);
+void signal_object_after (GtkButton *button, GParamSpec spec);
+void signal_first (GtkButton *button, GParamSpec spec);
+void signal_second (GtkButton *button, GParamSpec spec);
+void signal_extra (GtkButton *button, GParamSpec spec);
+void signal_extra2 (GtkButton *button, GParamSpec spec);
+
 /* Copied from gtkiconfactory.c; keep in sync! */
 struct _GtkIconSet
 {

gtk/tests/cellarea.c

@@ -78,6 +78,8 @@ test_iconview_object_new (void)
 typedef GtkIconView MyIconView;
 typedef GtkIconViewClass MyIconViewClass;
 
+GType my_icon_view_get_type (void);
+
 G_DEFINE_TYPE (MyIconView, my_icon_view, GTK_TYPE_ICON_VIEW)
 
 static void
@@ -234,6 +236,8 @@ test_combobox_object_new (void)
 typedef GtkComboBox MyComboBox;
 typedef GtkComboBoxClass MyComboBoxClass;
 
+GType my_combo_box_get_type (void);
+
 G_DEFINE_TYPE (MyComboBox, my_combo_box, GTK_TYPE_COMBO_BOX)
 
 static void
@@ -390,6 +394,8 @@ test_cellview_object_new (void)
 typedef GtkCellView MyCellView;
 typedef GtkCellViewClass MyCellViewClass;
 
+GType my_cell_view_get_type (void);
+
 G_DEFINE_TYPE (MyCellView, my_cell_view, GTK_TYPE_CELL_VIEW)
 
 static void
@@ -544,6 +550,8 @@ test_column_object_new (void)
 typedef GtkTreeViewColumn MyTreeViewColumn;
 typedef GtkTreeViewColumnClass MyTreeViewColumnClass;
 
+GType my_tree_view_column_get_type (void);
+
 G_DEFINE_TYPE (MyTreeViewColumn, my_tree_view_column, GTK_TYPE_TREE_VIEW_COLUMN)
 
 static void
@@ -698,6 +706,8 @@ test_completion_object_new (void)
 typedef GtkEntryCompletion MyEntryCompletion;
 typedef GtkEntryCompletionClass MyEntryCompletionClass;
 
+GType my_entry_completion_get_type (void);
+
 G_DEFINE_TYPE (MyEntryCompletion, my_entry_completion, GTK_TYPE_ENTRY_COMPLETION)
 
 static void

gtk/tests/rbtree.c

@@ -198,7 +198,7 @@ _gtk_rbtree_test_structure (GtkRBTree *tree)
   _gtk_rbtree_test_structure_helper (tree, tree->root);
 }
 
-void
+static void
 _gtk_rbtree_test (GtkRBTree *tree)
 {
   GtkRBTree *tmp_tree;

gtk/tests/stylecontext.c

@@ -313,7 +313,7 @@ test_style_property (void)
   g_object_unref (context);
 }
 
-void
+static void
 test_basic_properties (void)
 {
   GtkStyleContext *context;

gtk/tests/treestore.c

@@ -26,6 +26,8 @@
  *  - And we also need tests for creating these child levels, etc.
  */
 
+#include "treemodel.h"
+
 #include <gtk/gtk.h>
 
 static inline gboolean