COMP: Remove outdated conditionals/pragmas

1. Checking for ITK version, doesn't make
sense because internal to ITK source, ITK_VERSION_MAJOR
is always > 3.
2. MSC_VER pragma warnings in source files; centralized
in itkWin32Header.h

Change-Id: I11d414ade98655a357b93979e94e8d12c4f1f4ee
Merge topic 'RMOutdatedPragmasConditionals'

45bc1f7 COMP: Remove outdated conditionals/pragmas