Include <stdexcept> for std::out_of_bounds

And remove unused `used` statement.
Only output deaths once.

Note that this _has_ to be done in the visitor; post-processing cannot
determine cases such as death during pudge hook or death during mirana
jump by simple `uniq` filtering.
Merge pull request #13 from lucasb-eyer/fix-multiple-death-reports

Fix multiple death reports