BUF/BIO cleanup 4/99:

BUF/BIO cleanup 4/99:

Garbage-collect physio_proc_{enter,leave,init} because these functions
only existed for PC-98 compatibility reasons.  This commit is a NOP
and shouldn't make any operational difference.

The purpose of those functions was totally redundant, it just kept a
copy of buf->b_proc and other fields in a separately maintained TAILQ
list called physio_proc_head and physio_proc_feet corresponding to
physio_proc_enter/leave respectively.

The stub definitions and the machine/physio_proc.h header file will
disappear after the drivers using these functions are cleaned up.