bus: add new sd_bus_message_verify_type() and sd_bus_message_copy() API calls
bus: add a macro to simplify reading of UUIDs
timedate: handle more nicely if something or somebody keeps open /dev/rtc and thus blocks out everybody else

chrony is appears to keep the RTC open continuously these days which is
a bad idea, and /dev/rtc is a single-user device, which is a bad idea
too. Together both bad ideas mean that nobody else can access the RTC
anymore. That's something to fix, but in the meantime we should handle
this more gracefully.
rc-local: use access(X_OK) to check if files are executable

... and other modernizations.