Cleanup: reorganize doxygen modules

- Nest compositor pages under the compositor module
- Nest GUI, DNA/RNA & externformats modules under Blender.
- Remove modules from intern which no longer exist.
- Add intern modules (atomic, eigen, glew-mx, libc_compat, locale,
  numaapi, rigidbody, sky, utfconv).
- Use 'intern_' prefix for intern modules since some of the modules
  use generic terms such as locale & atomic.

intern/clog/CLG_log.h

@@ -14,11 +14,8 @@
  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
-#ifndef __CLG_LOG_H__
-#define __CLG_LOG_H__
-
 /** \file
- * \ingroup clog
+ * \ingroup intern_clog
  *
  * C Logging Library (clog)
  * ========================
@@ -68,6 +65,9 @@
  * - 4+: May be used for more details than 3, should be avoided but not prevented.
  */
 
+#ifndef __CLG_LOG_H__
+#define __CLG_LOG_H__
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */