lmtp: Ported to use lib-smtp/server. Implicitly fixes handling of multi-line replies from proxy backend. Implicitly adds support for mixing local and proxy recipients. Implicitly adds support for SMTP CHUNKING. RCPT failures are reported back to the client immediately, rather than waiting for the DATA command.

lmtp: Moved lmtp_anvil_init() from commands.c to main.c. It fits better there.

lmtp: Don't permanently allocate from data stack during init.

lmtp: Added lmtp_user_concurrency_limit setting. This allows limiting the number of concurrent deliveries to a single user. Useful in case one user is receiving a lot of mails and causing other deliveries to be delayed. If the limit is reached, Dovecot returns temporary failure error at DATA stage.

lmtp: Make core dumping work also after the first mail delivery.

lmtp proxy: Added support for DNS lookups. --HG-- branch : HEAD

Merged single and multi mail_storage_service_*() functions. --HG-- branch : HEAD

lib-master has now a global master_service variable that all binaries use. There should always be only one of them anyway. --HG-- branch : HEAD

Initial implementation of LMTP server. Master process doesn't yet execute it though. --HG-- branch : HEAD