[Dovecot] Compiler warnings in dovecot-2.1.2 and pigeonhole 0.3.0

[Tom Talpey]

I'm seeing a few warnings emitted when building for x86. They're pretty
obvious, but if you want the configure options etc, I can provide those.

In Dovecot 2.1.2 (I also see some of these in 2.1.1):

1) src/lib-index/mail-cache-fields.c

(comparison between two last_used fields)
mail-cache-fields.c: In function 'mail_cache_header_fields_read':
mail-cache-fields.c:406: warning: comparison between signed and unsigned

2) src/director/user-directory.c

(comparison with ioloop_time)
user-directory.c: In function 'user_directory_user_is_recently_updated':
user-directory.c:147: warning: comparison between signed and unsigned

3) src/replication/replicator/replicator-brain.c

(comparison with ioloop_time)
replicator-brain.c: In function 'doveadm_replicate':
replicator-brain.c:113: warning: comparison between signed and unsigned

4) src/replication/replicator/replicator-queue.c

(comparison with ioloop_time)
replicator-queue.c: In function 'replicator_queue_pop':
replicator-queue.c:201: warning: comparison between signed and unsigned

In Pigeonhole 0.3.0:

5) src/managesieve-login/client-authenticate.c

(passing size_t * not uoff_t *)
client-authenticate.c: In function 'managesieve_client_auth_read_response':
client-authenticate.c:214: warning: passing argument 3 of 
'i_stream_get_size' from incompatible pointer type