aout_freebsd.c

aout_freebsd.c
	Use bd_getdev() to work out a dev_t for the root device.
	Allow $rootdev to override $currdev as the root device.

biosdisk.c
	Save the slice table and disklabel when opening a disk.
	Add bd_getdev(), which attempts to return a dev_t corresponding
	to a given device.  Cases which it still doesn't get right:
	 - The inevitable da-when-wd-also-exists
	 - Disks with no slice table (the slice number is not set correctly)
	The first is difficult to get right, the second will be
	fixed in an upcoming commit.

comconsole.c
vidconsole.c
	getchar() should return an 8-bit value; some BIOSsen pack extra
	information in %eax.

libi386.h
	Remove some stale prototypes, add new ones.