Python API Docs: document when fields use mathutils types.

When accessing certain structure fields from Python, they return
mathutils types instead of generic arrays (this is based on subtype).

This exposes this information in the Python API documentation.

Differential Revision: https://developer.blender.org/D16626

doc/python_api/sphinx_doc_gen.py

@@ -1294,6 +1294,7 @@ def pycontext2sphinx(basepath):
 
             type_descr = prop.get_type_description(
                 class_fmt=":class:`bpy.types.%s`",
+                mathutils_fmt=":class:`mathutils.%s`",
                 collection_id=_BPY_PROP_COLLECTION_ID,
                 enum_descr_override=enum_descr_override,
             )
@@ -1446,6 +1447,7 @@ def pyrna2sphinx(basepath):
             identifier = " %s" % prop.identifier
 
         kwargs["class_fmt"] = ":class:`%s`"
+        kwargs["mathutils_fmt"] = ":class:`mathutils.%s`"
 
         kwargs["collection_id"] = _BPY_PROP_COLLECTION_ID
 
@@ -1565,6 +1567,7 @@ def pyrna2sphinx(basepath):
 
             type_descr = prop.get_type_description(
                 class_fmt=":class:`%s`",
+                mathutils_fmt=":class:`mathutils.%s`",
                 collection_id=_BPY_PROP_COLLECTION_ID,
                 enum_descr_override=enum_descr_override,
             )
@@ -1631,6 +1634,7 @@ def pyrna2sphinx(basepath):
 
                     type_descr = prop.get_type_description(
                         as_ret=True, class_fmt=":class:`%s`",
+                        mathutils_fmt=":class:`mathutils.%s`",
                         collection_id=_BPY_PROP_COLLECTION_ID,
                         enum_descr_override=enum_descr_override,
                     )