Change sysflags and oldflags to log as hex

[robmueller]

Currently sysflags and oldflags are logged as decimal, which makes them really hard to glace in the logs.

e.g. sysflags=<805306384>

If this was logged as hex instead, it would be a lot more obvious at a glance.

e.g. sysflags=<30000010>

Ok, so you still need to know the constants in mailbox.h rather well, but it's still easier to remember 8000000 = expunge, 4000000 = unlinked, 2000000 = archived, 1000000 = needs cleanup and decode 3 = 2 + 1 a lot quicker than the decimal version.