BUG: Fix itk_module_config for repeated calls

Fix use of _${ns}_${mod}_USED settings to block reporting a module more
than once in a single itk_module_config call.  Do not leak the
_${ns}_${mod}_USED settings outside a single call to itk_module_config
so that a future call to the macro with the same ${ns} will use a fresh
set of modules.

Change-Id: I422e415f45db877512a0dcd3c588d9f74d32f515
Ensure ITKDeprecated is always excluded from the default module list.

Since Slicer or any of the current extension [1] depend on ITKDeprecated,
this commit ensures that ITKDeprecated is always excluded from
the list of default module independently of the value of the
ITKV3_COMPATIBILITY option.

[1] At the time of this commit, the pull request removing ITKDeprecated
from the LASegmenter extension is pending. See https://github.com/ljzhu/LASegmenter/pull/2