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.

doc/doxygen/doxygen.intern.h

@@ -6,91 +6,90 @@
  *  as part of the normal development process.
  */
 
-/** \defgroup MEM Guarded memory (de)allocation
- *  \ingroup intern
+/* TODO: other modules.
+ * - `libmv`
+ * - `cycles`
+ * - `opencolorio`
+ * - `opensubdiv`
+ * - `openvdb`
+ * - `quadriflow`
  */
 
-/** \defgroup clog C-Logging (CLOG)
- *  \ingroup intern
- */
+/** \defgroup intern_atomic Atomic Operations
+ *  \ingroup intern */
 
-/** \defgroup ctr container
- *  \ingroup intern
- */
+/** \defgroup intern_clog C-Logging (CLOG)
+ *  \ingroup intern */
 
-/** \defgroup iksolver iksolver
- *  \ingroup intern
- */
+/** \defgroup intern_eigen Eigen
+ *  \ingroup intern */
 
-/** \defgroup itasc itasc
- *  \ingroup intern
- */
+/** \defgroup intern_glew-mx GLEW with Multiple Rendering Context's
+ *  \ingroup intern */
 
-/** \defgroup memutil memutil
- *  \ingroup intern
- */
+/** \defgroup intern_iksolver Inverse Kinematics (Solver)
+ *  \ingroup intern */
 
-/** \defgroup mikktspace mikktspace
- *  \ingroup intern
- */
+/** \defgroup intern_itasc Inverse Kinematics (ITASC)
+ *  \ingroup intern */
 
-/** \defgroup moto moto
- *  \ingroup intern
- */
+/** \defgroup intern_libc_compat libc Compatibility For Linux
+ *  \ingroup intern */
 
-/** \defgroup eigen eigen
- *  \ingroup intern
- */
+/** \defgroup intern_locale Locale
+ *  \ingroup intern */
 
-/** \defgroup smoke smoke
- *  \ingroup intern
- */
+/** \defgroup intern_mantaflow Manta-Flow Fluid Simulation
+ *  \ingroup intern */
 
-/** \defgroup string string
- *  \ingroup intern
- */
+/** \defgroup intern_mem Guarded Memory (de)allocation
+ *  \ingroup intern */
+
+/** \defgroup intern_memutil Memory Utilities (memutil)
+ *  \ingroup intern */
+
+/** \defgroup intern_mikktspace MikktSpace
+ *  \ingroup intern */
+
+/** \defgroup intern_numaapi NUMA (Non Uniform Memory Architecture)
+ *  \ingroup intern */
+
+/** \defgroup intern_rigidbody Rigid-Body C-API
+ *  \ingroup intern */
+
+/** \defgroup intern_sky_model Sky Model
+ *  \ingroup intern */
+
+/** \defgroup intern_utf_conv UTF-8/16 Conversion (utfconv)
+ *  \ingroup intern */
 
 /** \defgroup audaspace Audaspace
  *  \ingroup intern undoc
- *  \todo add to doxygen
- */
+ *  \todo add to doxygen */
 /** \defgroup audcoreaudio Audaspace CoreAudio
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audfx Audaspace FX
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audopenal Audaspace OpenAL
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audpulseaudio Audaspace PulseAudio
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audwasapi Audaspace WASAPI
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audpython Audaspace Python
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audsdl Audaspace SDL
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audsrc Audaspace SRC
- *
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audffmpeg Audaspace FFMpeg
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audfftw Audaspace FFTW
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audjack Audaspace Jack
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 /** \defgroup audsndfile Audaspace sndfile
- *  \ingroup audaspace
- */
+ *  \ingroup audaspace */
 
 /** \defgroup GHOST GHOST API
  * \ingroup intern GUI