SBBSecho doesn't expand sole-LFs in body text to CRLF

Linefeed characters are optional and should be ignored in FidoNet (per FTS-1), so messages stored in the message bases without carriage returns on new-lines don't necessarily view correctly on all FidoNet nodes/readers.

SBBSecho should have the option to convert sole-LFs in exported message bodies to either CRLF or just CR.