bpo-39136: Fixed typos (GH-17720)

funtion -> function; configuraton -> configuration; defintitions -> definitions;
focusses -> focuses; necesarily -> necessarily; follwing -> following;
Excape -> Escape,
diff --git a/Doc/c-api/structures.rst b/Doc/c-api/structures.rst
index 1bd769f..0c66138 100644
--- a/Doc/c-api/structures.rst
+++ b/Doc/c-api/structures.rst
@@ -350,7 +350,7 @@
    .. _pymemberdef-offsets:
 
    Heap allocated types (created using :c:func:`PyType_FromSpec` or similar),
-   ``PyMemberDef`` may contain defintitions for the special members
+   ``PyMemberDef`` may contain definitions for the special members
    ``__dictoffset__`` and ``__weaklistoffset__``, corresponding to
    :c:member:`~PyTypeObject.tp_dictoffset` and
    :c:member:`~PyTypeObject.tp_weaklistoffset` in type objects.