Removed the local include/OpenThreads and src/OpenThreads sources, as these are
now contained directly in the svn/osg/OpenSceneGraph/trunk, and introduced svn:extenals
to the OpenThreads? itself.
This changed has been made to make it possible from OpenSceneGraph users to use https
where checking out OpenSceneGraph svn, something that is not possible when using http
based externals.
This howevever, does introduce this https checkout issue to OpenThreads? itself, but given
the vastly much bigger OpenSceneGraph/OpenThreads? community than OpenThreads? only community
the numbers of users inconvinienced are far smaller (and may well not include
any developers whatsoever in fact...)
