BUG: Fix typo in PyGithub and python-smmap projects.

This commit properly sets the SETUPTOOLS lock variable introduced
in r23409 and addressing issue #3757.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23420 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Prevent windows build freeze when downloading setuptools 2.2

Updates setuptools from version 1.4.2 to 5.3

This commit fixes #3763 by ensuring a recent version of setuptools
is used by all projects. Having a recent version of setuptools in the
python path will prevent SimpleITK  (and other project) from trying
to download older setuptools will avoid the possible freeze.

This commit also patches the "setup.py" provided by pydicom to avoid
downloading an old version of distribute. This is done by removing the
first 3 lines of setup.py that were using an ancient distribute_setup.py.

Finally, after some testing recent version of setuptools (5.3 in the present
case) does NOT prevent incorrect update of "easy-install.pth" in case of
concurrent installs.
The issue distribute issue 389 [1] also mentioned in Slicer issue #3757 [2]
is still current.

[1] https://bitbucket.org/tarek/distribute/issue/389/concurrent-installations-can-lose-updates
[2] http://www.na-mic.org/Bug/view.php?id=3757

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23421 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: Improve comment associated with lock variable.

This commit updates the text illustrating why a lock variable should
be used. For reference, the lock variable has been introduced in r23409.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23422 3bd1e089-480b-0410-8dfb-8563597acbee