Strip trailing whitespace

[r-barnes]

Every pull request I make causes a large number of spurious changes because my editor strips trailing whitespace.

This PR removes all such trailing whitespace from the repository, which should make it easier for folks to contribute small PRs in the future.

I produced this PR by running:

find . -iname "*.c" -type f -print0 | xargs -0 perl -pi -e 's/ +$//'
find . -iname "*.cpp" -type f -print0 | xargs -0 perl -pi -e 's/ +$//'
find . -iname "*.h" -type f -print0 | xargs -0 perl -pi -e 's/ +$//'

but almost all code editors can be configured to automatically strip trailing whitespace when the file is saved.

[sahrk]

I ran this on the latest master and will endeavor to do so in the future.