Qmail-SQL - Maildir++ support

This patch adds maildirquota (Maildir++) support to qmail-pop3d, qmail-local and sqlcreatehomedir. It was created because when using some other Maildir++ enabled programs (Maildrop, Courier-IMAP, ...) which access the same Maildir, then quota information is not modified by qmail-pop3d after deleting message and by qmail-local after local delivery.\r\n\r\nThis patch is tailored to fit to Qmail-SQL (SQL enabled Qmail), but it may be used on original qmail with few modifications.\r\n\r\nNote: Qmail-SQL uses it's own quota mechanism in qmail-local by calling "du' (disk usage) on user's Maildir every time, which is not very effective. This mechanism works with sizes in KILOBYTES, but Maildir++ quota mechanism works with BYTES, so you have to update quota column in your qmail table/database.\r\n\r\nThis patch was inspired by the Maildir++ patch by Bill Shupp, but his patch used old maildirquota functions. This patch uses same maildirquota functions as Courier-IMAP 2.2.1 does.\r\n\r\nSee the Maildir++ specification by Sam Varshavchik on www.courier-mta.org.