Since commit 238d0d1 (Improve consistency for inserting new headlines)
a few minor inconsistencies were introduced to heading creation with
the control key, A.K.A. org-insert-heading-respect-content.  This
patch resolves those subtle "bugs".

This patch changes org-insert-heading-respect-content so that it:

 - Creates a new heading even if point is in a plain list
   (force-heading is set to true, behavior before 238d0d1)
 - If the previous heading was closed, keep it closed
   (keeps the previous heading in the state it was before C-RET)

It also includes changes for org-insert-todo-heading and the OrgMode
manual.

Thanks Carsten for making the changes in 238d0d1 for me.  With the
attached patch, heading creation is now perfect (for me at least ;).