Cleanup: move doc-strings into headers, remove duplicates

In some cases move implementation details into the function body.

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);