STYLE: Remove old cmake < 2.8.4 specific code

We are requiring at least cmake 2.8.6

Change-Id: Ia34c77bdfa866c4eba58f1b3f28d454e095a8851
Merge topic 'RemoveCmake2.8.4Code'

a43271f9 STYLE: Remove old cmake < 2.8.4 specific code
Merge branch 'wrap-blockMatchingImageFilter-types_release' into release

Change-Id: Id6f5675ab661f4fc26dd698efad5158c3f37f555
Merge branch 'release'

Change-Id: I99a6f0e4fbb68bb89f63d372e8456e063de265d4
BUG: Do not perform itk_download_attempt_check when not building ITK.

When processing WrapITKConfig.cmake, for example with a find_package(WrapITK),
it will include ConfigureWrapping.cmake, which in turn includes

Wrapping/Generators/GccXML/CMakeLists.txt
Wrapping/Generators/SwigInterface/CMakeLists.txt

In this case, the itk_download_attempt_check macro is not defined, but the
check is not required.  Only perform the download check when building ITK,
which is detected by the ITK_BINARY_DIR variable, which is generated by

  project(ITK)

in the top level CMakeLists.txt.

ITK-3319

Change-Id: I372357eefc48abe783b5fb59a1a55d3b3a050cfb
Merge topic 'WrapITKitk_download_attempt_release'

825aa58a BUG: Do not perform itk_download_attempt_check when not building ITK.