[gtkmm] SpinButton: Move INPUT_ERROR constant into class.

[Murray Cumming <murrayc src gnome org>]

commit 87032117f08d381dba854088d6f0f64bded81171
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Apr 27 14:01:44 2017 +0200

    SpinButton: Move INPUT_ERROR constant into class.

 gtk/src/spinbutton.hg |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)
---
diff --git a/gtk/src/spinbutton.hg b/gtk/src/spinbutton.hg
index 852767f..1eafff2 100644
--- a/gtk/src/spinbutton.hg
+++ b/gtk/src/spinbutton.hg
@@ -29,9 +29,6 @@ _CC_INCLUDE(gtk/gtk.h)
 _WRAP_ENUM(SpinButtonUpdatePolicy, GtkSpinButtonUpdatePolicy)
 _WRAP_ENUM(SpinType, GtkSpinType)
 
-/** @ingroup gtkmmEnums */
-enum { INPUT_ERROR = -1 };
-
 class Adjustment;
 
 /** numeric Entry with up/down buttons
@@ -92,6 +89,13 @@ public:
 
   _WRAP_METHOD(void update(), gtk_spin_button_update)
 
+  /** Constant to return from a signal handler for the input
+   * signal in case of conversion failure.
+   *
+   * @ingroup gtkmmEnums
+   */
+  enum { INPUT_ERROR = -1 };
+
   _WRAP_SIGNAL(int input(double* new_value), "input")
   _WRAP_SIGNAL(bool output(), "output")
   _WRAP_SIGNAL(void wrapped(), "wrapped")