Fix most of the deprecated function calls that could easily be fixed by very simple sed scripts.

I ran the following and then did some manual fixups:
find -name '*.rs' -exec sed -i 's/.mut_iter()/.iter_mut()/' '{}' ';'
find -name '*.rs' -exec sed -i 's/.move_iter()/.into_iter()/g' '{}' ';'
find -name '*.rs' -exec sed -i 's/.push_char(/.push(/' '{}' ';'
find -name '*.rs' -exec sed -i 's/.push_all_move(\(.*\));/.extend(\1.into_iter());/' '{}' ';'
find -name '*.rs' -exec sed -i 's/Vec::from_slice(\(.*\));/\1.to_vec();/' '{}' ';'
find -name '*.rs' -exec sed -i 's/.mut_last()/.last_mut()/' '{}' ';'