(BWDIC!) Extend semantics of -a and `~@' (bwdic!); attachments for `~^'..
Unify all -- now four! -- ways of attaching by inventing a new
syntax:
FILENAME[=INPUT-CHARSET[#OUTPUT-CHARSET]]
where input- and output-character-set may be empty or - to denote
*ttycharset* and a normal *sendcharsets* iteration, respectively.
(Thus one can now specify an input character set and can
nonetheless end up with *sendcharsets* iteration, or even specify
a designated target set!)
Add attachment support to the reliably scriptable `~^' command
escape.