convert: handle trailing slashes in filemap better (issue3124)

tests: remove test-casecollision-i18n.t The result of this test is quite suspect. Remove it for now as it now correctly breaks on HFS+.

posix: fix HFS+ percent-encoding folding We use 'ignore' rather than 'replace' so we don't have to deal with u+FFFD in UTF-8 round-trip.

mail: use quoted-printable for mime encoding to avoid too long lines (issue3075) Quoted-printable was already used for the more critical patch mails, so it should be fine for everything else as well.

notify: add option for writing to mbox This makes it possible to test how the mails that are sent _really_ look like.

mail: mbox handling as a part of mail handling, refactored from patchbomb

patchbomb: minor refactoring of mbox functionality, preparing for move This allows reuse of the mbox functionality but causes minor changes in the patchbomb console output when writing to a mbox.