This commit updates build system of external projects and Slicer to address
warnings like the following:

  CMake Warning (dev) at CMakeLists.txt:393 (FIND_PACKAGE):
    Policy CMP0074 is not set: find_package uses <PackageName>_ROOT variables.
    Run "cmake --help-policy CMP0074" for policy details.  Use the cmake_policy
    command to set the policy and suppress this warning.

    CMake variable ZLIB_ROOT is set to:

      /path/to/zlib-install

    For compatibility, CMake is ignoring the variable.
  This warning is for project developers.  Use -Wno-dev to suppress it.



List of ITK changes:

$ git shortlog a44f430b3e..87f5d83f15 --no-merges
Jean-Christophe Fillion-Robin (1):
      COMP: Set CMP0074 to NEW [backport]


List of LibArchive changes:

$ git shortlog 944ab1d0..0737ce70 --no-merges
Jean-Christophe Fillion-Robin (1):
      cmake: Set CMP0074 to NEW


List of curl changes:

$ git shortlog 0722f23..c5e0ea129 --no-merges
Simon Warta (1):
      [backport] cmake: Replace invalid UTF-8 byte sequence

Note that the fix has not been integrated to curl because the version
used is using its own FindZLIB module that is not using ZLIB_ROOT.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@27609 3bd1e089-480b-0410-8dfb-8563597acbee