Cleanup: move doc-strings into headers, remove duplicates

In some cases move implementation details into the function body.

source/blender/python/mathutils/mathutils.c

@@ -511,6 +511,7 @@ int EXPP_FloatsAreEqual(float af, float bf, int maxDiff)
 
 /*---------------------- EXPP_VectorsAreEqual -------------------------
  * Builds on EXPP_FloatsAreEqual to test vectors */
+
 int EXPP_VectorsAreEqual(const float *vecA, const float *vecB, int size, int floatSteps)
 {
   int x;
@@ -570,9 +571,10 @@ int _BaseMathObject_CheckCallback(BaseMathObject *self)
   return -1;
 }
 
-/* use macros to check for NULL */
 int _BaseMathObject_ReadCallback(BaseMathObject *self)
 {
+  /* NOTE: use macros to check for NULL. */
+
   Mathutils_Callback *cb = mathutils_callbacks[self->cb_type];
   if (LIKELY(cb->get(self, self->cb_subtype) != -1)) {
     return 0;
@@ -636,7 +638,8 @@ void _BaseMathObject_RaiseNotFrozenExc(const BaseMathObject *self)
       PyExc_TypeError, "%s is not frozen (mutable), call freeze first", Py_TYPE(self)->tp_name);
 }
 
-/* BaseMathObject generic functions for all mathutils types */
+/* #BaseMathObject generic functions for all mathutils types. */
+
 char BaseMathObject_owner_doc[] = "The item this is wrapping or None  (read-only).";
 PyObject *BaseMathObject_owner_get(BaseMathObject *self, void *UNUSED(closure))
 {

source/blender/python/mathutils/mathutils_geometry.c

@@ -1804,6 +1804,7 @@ static struct PyModuleDef M_Geometry_module_def = {
 };
 
 /*----------------------------MODULE INIT-------------------------*/
+
 PyMODINIT_FUNC PyInit_mathutils_geometry(void)
 {
   PyObject *submodule = PyModule_Create(&M_Geometry_module_def);

source/blender/python/mathutils/mathutils_interpolate.c

@@ -100,6 +100,7 @@ static struct PyModuleDef M_Interpolate_module_def = {
 };
 
 /*----------------------------MODULE INIT-------------------------*/
+
 PyMODINIT_FUNC PyInit_mathutils_interpolate(void)
 {
   PyObject *submodule = PyModule_Create(&M_Interpolate_module_def);

source/blender/python/mathutils/mathutils_noise.c

@@ -1096,6 +1096,7 @@ static struct PyModuleDef M_Noise_module_def = {
 };
 
 /*----------------------------MODULE INIT-------------------------*/
+
 PyMODINIT_FUNC PyInit_mathutils_noise(void)
 {
   PyObject *submodule = PyModule_Create(&M_Noise_module_def);