Move i386 to generic RTC handling code.

Move i386 to generic RTC handling code.

Make clock_if.m and subr_rtc.c standard on i386

Add hints for "atrtc" driver, for non-PnP, non-ACPI systems.
NB: Make sure to install GENERIC.hints into /boot/device.hints in these!

Nuke MD inittodr(), resettodr() functions.

Don't attach to PHP0B00 in the "attimer" dummy driver any more, and remove
comments that no longer apply for that reason.

Add new "atrtc" device driver, which handles IBM PC AT Real Time
Clock compatible devices using subr_rtc and clock_if.

This driver is not entirely clean: other code still fondles the
hardware to get a statclock interrupt on non-ACPI timer systems.

Wrap some overly long lines.

After it has settled in -current, this will be ported to amd64.

Technically this is MFC'able, but I fail to see a good reason.