lib-imap: Add imap_write_arg() to write only a single arg

lib-imap: Add imap_write_args_for_human()

Removed all the "enum foo;" declarations. They didn't seem to be very standard. Old gcc versions warn about them and C++ code doesn't like them.

Marked functions parameters that are allowed to be NULL. Some APIs were also changed. The non-obvious APIs where NULL parameter was changed to "" are master_service_init() and auth_master_user_list_init(). These checks can currently be enabled only on a patched clang: http://llvm.org/bugs/show_bug.cgi?id=6786

Added imap_parse_system_flag(). --HG-- branch : HEAD

Renamed imap_args_to_str() to imap_write_args() and added a new imap_args_to_str(). --HG-- branch : HEAD

Added imap_args_to_str() --HG-- branch : HEAD

Initial CONDSTORE support. --HG-- branch : HEAD

Compiler warning fix. --HG-- branch : HEAD

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Removed unneeded enum declarations. --HG-- branch : HEAD

compiler warning fix --HG-- branch : HEAD

Initial support for keywords. Syncing to mbox/maildir doesn't work yet. --HG-- branch : HEAD

Broke mailbox_sync() into iterator. --HG-- branch : HEAD

s/custom flags/keywords/ --HG-- branch : HEAD

importing new index code. mbox still broken. --HG-- branch : HEAD

Maildir syncing works now without requiring base filenames to be in index cache file. Also message flag updates with +FLAGS and -FLAGS works correctly now if another client had just changed it's flags. --HG-- branch : HEAD

API change for updating message flags. --HG-- branch : HEAD

Naming style changes, finally got tired of most of the typedefs. Also the previous enum -> macro change reverted so that we don't use the highest bit anymore, that's incompatible with old indexes so they will be rebuilt. --HG-- branch : HEAD

Use unsigned char* when accessing non-NUL terminating strings. Compiler warnings would then notify about accidentally passing them to functions which require them NUL-terminated. Changed a few functions to use void* to avoid unneeded casting. --HG-- branch : HEAD

Rewrote rfc822-tokenize.c to work one token at a time so it won't uselessly take memory, maybe also a bit faster. This caused pretty large changes all around. Also moved all string (un)escaping code to lib/strescape.c. --HG-- branch : HEAD

MailStorage interface change. We now let storage call several sync-functions whenever it wants instead of forcing it through sync() function. This now allows us to send client FLAGS and PERMANENTFLAGS messages whenever new custom flags are added. Also EXPUNGE command now goes nicely through expunge() function (which CLOSE used) instead of through flag in sync(). "Out of disk space" alert is also sent now whenever it happens, before it was sent only when opening mailbox. Message set parser now complains when referencing mail sequences outside the possible range. Modify log before sent flags/expunges changes to client even if it didn't know about those messages yet. Also some other smaller cleanups. Beginnings of fixing APPEND and COPY when trying to store mails into selected mailbox. Before this didn't work too well or simply broke things. Still broken, needs a bit more changes.. --HG-- branch : HEAD

Initial revision --HG-- branch : HEAD