Whitespace cleanup.

Take 2. Supersedes #572.

```
$ find . -type f -name '*.idr' -exec sed --in-place 's/[[:space:]]\+$//' {} \+
$ find . -type f -name '*.hs' -exec sed --in-place 's/[[:space:]]\+$//' {} \+
$ find . -type f -name '*.lidr' -exec sed --in-place 's/[[:space:]]\+$//' {} \+
$ find test/ -type f -name '*' -exec sed --in-place 's/[[:space:]]\+$//' {} \+
```