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, 1 insertions, 0 deletions

diff --git a/interimap.sample b/interimap.sample
index 86d41dd..b0f619a 100644
--- a/interimap.sample
+++ b/interimap.sample
@@ -2,6 +2,7 @@
 #list-mailbox = "*"
 list-select-opts = SUBSCRIBED
 ignore-mailbox = ^virtual/
+#use-binary = YES
 
 [local]
 type = tunnel