Clear up trailing whitespace

We have ci checks for trailing whitespace, but the current code has many violations of this policy. Correct these in a big commit so there's less confusion. There should be no functional changes.

This addresses everything reported by

git diff-tree --check $(git hash-object -t tree /dev/null) HEAD

except for doc/opus_update.patch which I wanted to preserve as-is for historical reference.

With these changes the repo does pass git diff-tree --check v1.2 HEAD which covers a fair bit of recent history.

While this should address the github ci failure directly, also update it to compare against the default branch link the gitlab test does so the two systems perform the same evaluation.