filter/vger: kill trailing newlines aggressively
PublicInbox::MboxReader->(mboxrd|mboxo) only deletes the last
trailing newline, not every single trailing newline like
InboxWritable->import_mbox does.
Testing PublicInbox::MboxReader->mboxrd (next commit) with
scripts/import_vger_from_mbox on the LKML archive I got 2018 for
v2 development; this difference was responsible for a single
spam message(*) from out of
2722831 not being filtered correctly
and returning a different result.
(*) dated 2014-08-25