Add the missing cogl_is_context() function

This was missing from the CoglContext header.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

cogl/cogl-context.h

@@ -77,6 +77,21 @@ void
 cogl_android_set_native_window (ANativeWindow *window);
 #endif
 
+/**
+ * cogl_is_context:
+ * @object: An object or %NULL
+ *
+ * Gets whether the given object references an existing context object.
+ *
+ * Return value: %TRUE if the handle references a #CoglContext,
+ *   %FALSE otherwise
+ *
+ * Since: 1.10
+ * Stability: Unstable
+ */
+gboolean
+cogl_is_context (void *object);
+
 G_END_DECLS
 
 #endif /* __COGL_CONTEXT_H__ */

doc/reference/cogl-2.0-experimental/cogl-2.0-experimental-sections.txt

@@ -74,6 +74,7 @@ cogl_wayland_display_set_compositor_display
 
 <SUBSECTION>
 cogl_context_new
+cogl_is_context
 cogl_context_get_display
 
 <SUBSECTION>