- Changed MSG_TRUNCFILE to MSG_MIMEATTACH
- Removed unused netattr bit definitions.

MIME-encoded/embedded attachments.
We probably will want to do this for SMTP-posted messages (to subs) too.

don't care about filenames.
smb/mime_getattachment() now supports filenames with spaces in them. If we need
to strip or convert to short filenames, do that in the application/script code,
not in smblib.

indicate that a message's body text contains one or more MIME-encoded/embedded
attachments - so that entities won't have to parse the message headers/body
to determine whether or not a message has MIME-attachments.

*_net_type hfield has a value of 0 (NET_NONE) - according to smbdefs.h.

be shown at the top of the screen or relative to the bottom of the header.

console.msghdr_top_of_screen):
a hack to let scripts know whether the most-recently displayed message header
was displayed on the top of the terminal screen (or not). This allows us to
show avatars at the top of the screen when the header is up there, rather than
relevative to the bottom of the header (the pos can vary, depending on stuff).

strrchr() here to find terminating chars (quotes, parens, brackets).
e.g. '"Joe Shmoe" <joe@shmoe.com>, "Fred Smith" <fred@smith.org>'
would be parsed as 'Joe Shmoe" <joe@shmoe.com>, "Fred Smith'.

'data_length', but not always (e.g. may include text from some header
fields, excludes any non-text data fields).
Mark 'data_length' msg header property as read-only.

back in 1993, but were never needed/used.

header fields. Eliminate smb_getcontenttype() - now unnecessary.

the string being passed around.

or NULL if not relevant (not a MIME-encoded message).
Added smb_countattachments(): returns the number of file attachments in a
MIME-encoded message.
Added SMBMSGTXT_NO_TAILS definition to be used in place of '0' for
common smb_getmsgtxt() mode argument value.
The amount of white-space after "Content-Type:" and the content-type value
is now more flexible (0 or +1 spaces/tabs are fine).

sendfile() no longer logs "attachment" when a file description is provided.

download_file_attachments() and expose via new JS "bbs" method. Currently
this only reall works for the mail base.

since the smb_t already contains a subnum and we were passing a pointer to the
sbbs_t::smb to lower-level called-functions anyway.
Let's not mix-up class-scope with function arguments.

Fix the missing carriage-returns in the shell (bash) prompts by always building with the stderr logging
support (in *nix builds) - but run-time disable as desired via EX_NOLOG option. I've been wanting to get
rid of that "XTERN_*" macro for a long time anyway (it's "XTRN" damn-it!). :-)

Added EX_NOLOG to *nix shell mode - don't log the shell output.

- Renamed EX_INR and EX_OUTR to EX_STDIN and EX_STDOUT
  (with duplicate variables for backwards compatibility)
- Removed long-obsolete EX_OUTL, EX_SWAP
- Added (new) EX_NOLOG

intercepted output to stderr won't be logged.

Since QUOTEWRAP *is* used, just define that bit flag specifically.

list (smb_list) for thread-safe SMB stack storage.

and frankly could cause all kinds of havok with multiple thread (e.g. nodes)
pushing and popping SMB's concurrently. eek.

More use of get_index() if available, to help speed things up a bit.  Also, made a further optimization: when checking a sub-board if it has polls, check in reverse rather than forward.  Since polls & voting is a relatively recent feature in Synchronet, hopefully it should finish faster going in reverse.