Initial commit of recent changes to make DEV_BSIZE go away.

Runs on i386, needs work on other arch's. Main kernel routines should be
fine, but a number of the stand programs need help.

cd, fd, ccd, wd, and sd have been updated. sd has been tested with non-512
byte block devices. vnd, raidframe, and lfs need work.

Non 2**n block support is automatic for LKM's and conditional for kernels
on "options NON_PO2_BLOCKS".
DEF_BSIZE is right for raidsize().
Pull up to last week's -current.
Pull up to last week's -current.
DEV_BSIZE -> DEF_BSIZE.