g/c leftover local prototypes

no functional change

actually commit the code changes too (for previous commit)

Nothing MD about "int spldepth;", so put it into kernel.c

remove bmk_ prefix from routines private to platform/hw

print exception-causing rip also for divide-by-zero

hw: Consolidate clock-related code

This commit consolidates the common clock-related functions for the x86
and amd64 hw platform into platform/hw/arch/x86/clock.c.

No functional change intended.

install trap handlers from i386 (shared code with amd64)

lidt and ltr belong to locore.S, not intr.S

move timer init code into x86 common

remember to rename also amd64 calls in previous

Separate some x86-specific bits from the bmk_cpu interfaces.

bmk_cpu_foo -> bmk_x86_foo

Start unifying i386 and amd64 common bits into x86.

Install TSS for amd64

Makes the mpg123 unikernel work as amd64 on my laptop (i.e. real
bare metal instead of just qemu)

install some more trap handler to get diagnostic info

add initial support for amd64