mbox: Added more (and earlier) detection for errors in mbox istreams.

Set input stream names for mail file streams. --HG-- branch : HEAD

mbox: Don't cache mbox state after it has been unlocked. --HG-- branch : HEAD

mbox: Log mbox file path for "Unexpectedly lost .." errors. --HG-- branch : HEAD

mbox: If we detect corrupted cached offsets/sizes, make sure the mbox gets resynced. --HG-- branch : HEAD

mbox: Don't stop at From_-lines in the message bodies. Use Content-Length: header to figure out if it belongs to a message body or not. --HG-- branch : HEAD

Removed MAILBOX_OPEN_MBOX_ONE_MSG_ONLY flag and handling. Raw storage replaced its functionality. --HG-- branch : HEAD

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

Removed memory pool parameter from iostreams. Default pool was almost always used, and the stream usually required destroying anyway so it didn't even make freeing memory easier. --HG-- branch : HEAD

Fixes to handling CRLF linefeeds in mboxes. --HG-- branch : HEAD

Added MAILBOX_OPEN_MBOX_ONE_MSG_ONLY flag for mailbox_open() which makes it ignore all but the first From-line in a mbox. This kludge is required for deliver which builds a temporary mbox stream from the input. Later it should be fixed to use some plain-mailbox format instead of mbox. --HG-- branch : HEAD

Added "bool" type and changed all ints that were used as booleans to bool. --HG-- branch : HEAD

i_stream_sync() replaced istream_raw_mbox_flush(). Use i_stream_stat() instead of fstat() directly. Now we have the possibility to use istreams as read-only mboxes. --HG-- branch : HEAD

istream-raw-mbox now sets stream->eof when it's at the end of message to fix some issues elsewhere. --HG-- branch : HEAD

Removed istream.disconnected, it's too much of a special case and the only place where it's needed will be removed soon. Added istream.eof back, it's more useful. --HG-- branch : HEAD

Added istream_raw_mbox_is_eof() and fixed updating UIDVALIDITY in index --HG-- branch : HEAD

Complain if file isn't in mbox format. Complain if From-line wasn't found from expected location. Parser should handle now correctly any kind of mbox no matter how corrupted. --HG-- branch : HEAD

several fixes and optimizations. --HG-- branch : HEAD

mbox rewriting is almost working - the hard part is done. --HG-- branch : HEAD

mbox code compiles again, but syncing is only partially implemented so accessing mboxes fails.. Also some cleanups to index-storage and maildir code. --HG-- branch : HEAD

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