Fix `org-outline-overlay-data' marker insertion-type
* org.el (org-outline-overlay-data): Set the insertion-type of end
bound marker of the function to t (means marker advances when you
insert text at it)
This is to conserve outline visibility property when changes are made
at the end bound of the data.
For example: try `org-babel-execute-subtree' on a folded outline:
The new result will be shown after the folded part of the outline
whereas the outline body should not be visible.