1] Replace gcc atomic intrinsics with the correct intrinsics based on the platform.
2] Fix use of incorrect Export macros.

Change-Id: If13ecbaea82e47f01c462db494a370c427ca5e6d

Used the following command:

find . \( -iname *.h -and -type f \) -exec perl -pi -w -e 's/__vtk(.*)_h/vtk$1_h/g;' {} \;

Fixes many, but not all, clang -Wreserved-id-macro warnings.

Change-Id: I694ff053cb204c70e37b261296f496064d91fc07

Added example of multi-threaded streaming using executives.

Change-Id: I8c94b78e36fe94de94533b5b97580b6b2560e97e