Treat permanent delivery errors as temporary (configurable).

Treat permanent delivery errors as temporary (configurable).

Fetchmail no longer drops permanently undelivered messages by default,
to match historic documentation.  It does this by adding a new
"softbounce" option, see below.
Fixes Debian Bug#471283, demotes Debian Bug#494418 to wishlist.

There is a new "softbounce" global option that prevents the deletion of
messages that have not been forwarded.  It defaults to "true" for
fetchmail 6.3.X in order to match historic documentation.  This may
change its default in the next major release.

NOTE: untested.

svn path=/branches/BRANCH_6-3/; revision=5315