ENH: Update ITKv4: Fix compiling with gcc8

Among other improvements, it allows building VNL with gcc8, getting rid of error:

"Dunno about this gcc"

Complete list of changes

$ git shortlog f9ae0a051440b67..bc0d1723cb4442be2f7 --no-merges

Bradley Lowekamp (5): COMP: Use anonymous namespace for internal linkage COMP: Update SimpleITKFilters for dependency issues BUG: Add missing extensions to ImageIO BUG: Add specification of OutputImage Type for TobogganImageFilter BUG: Prevent concurrent read/write in output image

Francois Budin (1): BUG: Initializes CMAKE_DEBUG_POSTFIX to be empty

Jean-Christophe Fillion-Robin (3): BUG: Prevent gdcm "missing implementation" error on macOS STYLE: Refactor support of itkFloatingPointExceptions implementations BUG: Support FPE on macOS without "feenableexcept" function

Jon Haitz Legarreta Gorroño (1): ENH: Add Python wrap file to itk::MultiResolutionPDEDeforableRegistration.

Martino Pilia (1): BUG: fix itkFormatWarning in Python wrapping

Matthew McCormick (9): ENH: Add wrapping for BSplineTransformInitializer COMP: Do not use absolute path to TestBigEndian.cmake in GDCM COMP: Enable pthreads shim with Emscripten BUG: Allow module examples to be enabled when built externally ENH: Ensure external module examples get added to current build tree COMP: Work around RegionGrow2DTest compiler error on ppc64le BUG: Wrap long long instead of long COMP: Detect Linux in itkMemoryUsageObserver.h on Alpine Linux COMP: Wrap MultiResolutionPDEDeformableRegistration for Pyramid filter types

Niels Dekker (1): COMP: Worked around endless VS2015 Release compilation on Math::Floor

Pablo Hernandez-Cerdan (1): COMP: Fix VNL to compile with gcc8.

Sean McBride (5): STYLE: arranged/alphabetized things to make subsequent changes reviewable COMP: Fixed some missing name mangling of libTIFF symbols BUG: fixed crash on macOS under guardmalloc from RunOSCheck() COMP: Mangle HDF5 symbol names COMP: fix warning about implicit double to bool conversion