add a replacement API for PyCObject, PyCapsule #5630

All stdlib modules with C-APIs now use this.

Patch by Larry Hastings
diff --git a/Doc/c-api/concrete.rst b/Doc/c-api/concrete.rst
index 2ba0833..d1fdec0 100644
--- a/Doc/c-api/concrete.rst
+++ b/Doc/c-api/concrete.rst
@@ -101,6 +101,7 @@
    descriptor.rst
    slice.rst
    weakref.rst
+   capsule.rst
    cobject.rst
    cell.rst
    gen.rst