Add support for the Binary Content extension [RFC3516].

Unfortunately as of Debian Wheezy it doesn't work for Dovecot with
COMPRESS=DEFLATE [RFC4978] and non-synchronizing literals.

    perl -e 'use Compress::Raw::Zlib;
             print "a COMPRESS DEFLATE\r\n";
             sleep 1;
             my $d = new Compress::Raw::Zlib::Deflate( -WindowBits => -15 );
             $d->deflate("b APPEND TRASH ~{1+}\r\nx\r\n", my $buf);
             print $buf;
             $d->flush($buf, Z_SYNC_FLUSH);
             print $buf;
             sleep 1;
    ' | /usr/lib/dovecot/imap
    imap(guilhem): Panic: stream doesn't support seeking backwards

Interestingly, it works just fine for non-binary literals:

    perl -e 'use Compress::Raw::Zlib;
             print "a COMPRESS DEFLATE\r\n";
             sleep 1;
             my $d = new Compress::Raw::Zlib::Deflate( -WindowBits => -15 );
             $d->deflate("b APPEND TRASH {1+}\r\nx\r\n", my $buf);
             print $buf;
             $d->flush($buf, Z_SYNC_FLUSH);
             print $buf;
             sleep 1;
    ' | /usr/lib/dovecot/imap

However I can't reproduce the problem Dovecot 2.2.18 and Debian Sid (but
it doesn't help to install Dovecot from testing to my Wheezy box.)

1 files changed, 12 insertions, 0 deletions

diff --git a/interimap.1 b/interimap.1
index dc3b49b..e552351 100644
--- a/interimap.1
+++ b/interimap.1
@@ -324,6 +324,18 @@ Whether to redirect \fIcommand\fR's standard error to \(lq/dev/null\(rq
 for type \fItype\fR=tunnel.
 (Default: \(lqNO\(rq.)
 
+.TP
+.I use-binary
+Whether to use the Binary Content extension [RFC3516] in FETCH and
+APPEND commands.
+This is useful for binary attachments for instance, as it avoids the
+overhead caused by base64 encodings.  Moreover if the IMAP COMPRESS
+extension is enabled, full flush points are placed around large non-text
+literals to empty the compression dictionary.
+This option is only available in the default section, and is ignored if
+either server does not advertize \(lqBINARY\(rq in its capability list.
+(Default: \(lqYES\(rq.)
+
 .SH KNOWN BUGS AND LIMITATIONS
 
 .IP \[bu]