remove queue_message_remove_incoming() function: deleting an incoming
messgae should go through the backend anyway.
add QOP_FD_RW back to let the backend handle the message as it wants and
remove the need for all backends to create a /incoming/<msgid> directory.
fix quoting
implement queue_compress_file() as a helper function.
- avoid 1 stat() call *at least* per envelope
- store pid in struct smtpd to avoid calling getpid() every now and then
remove envelopes dir and use an envelope count instead
- use uintptr_t for using pointers as counter.
- fix counting in QOP_WALK
Merge branch 'master' into remove-envelope-dir

Conflicts:
	smtpd/queue_fsqueue.c
remove PATH_ENVELOPES and make queue_envelope_incoming_path static
in queue_fsqueue.c
Merge branch 'master' into queue-api
call queue_compress_file from backend if needed.
smtp process sends the data line to the queue which does the final
write.
make queue walk work again
Merge branch 'master' into queue-api
Merge branch 'master' into issue111-aliases-quoting
use safe_fclose() in commit.
fix expand and add regress test
add a strip function and use ist when splitting expand lines
text_to_expandnode needs a normalized input.
make aliases_expand_include user expand_line.
Merge branch 'master' into queue-api