This will allow additional information about the availability
and capabilities of extra generators to be queried without
actually creating them.
Instead of a static NewFactory() method like the main generator
factories have, use a static GetFactory() method to get a pointer to a
statically allocated extra generator factory. This simplifies memory
management.
Run the `Utilities/Scripts/clang-format.bash` script to update
all our C++ code to a new style defined by `.clang-format`.
Use `clang-format` version 3.8.
* If you reached this commit for a line in `git blame`, re-run the blame
operation starting at the parent of this commit to see older history
for the content.
* See the parent commit for instructions to rebase a change across this
style transition commit.