dragon: fix memcpy prototype and implementation
dragon: SAM implementation of the user memory copier
dragon: use usermem_sam

This provides a different implementation of the SAM copier routines that do
not touch the stack at awkward moments
6809: remove debug from lowlevel code, add more compiler glue
dragon: update the configuration file

Remove usermem_c bits
vt: go back to memcpy

We do need to switch to a memmove, but now we've fixed memcpy we can just
tag it as a TODO. Reverse scroll is busted on dragon due to this
start: put the termios init data into const

That way we've got more chance of discarding it
6809: Switch to -Os

We've updated the helpers so can now do this.

A minimal build 6809 image currently weighs in at 24K code, 8K data. Some
of this is the CPU, some the calling conventions, and some gcc.
devio: tty queue functions are really unsigned char

gcc cares so quieten it down
time_t: use a 32bit pair in kernel

While SDCC has a full 64bit longlong the other compilers are sadly lacking
at the moment. For the kernel the easiest thing to do is to work in 32bit
chunks, it's not as if the CPU can do better than 16bits at a go anyway
start: remove bogus copy of const object - make it static const
usermem_sam: Bug fixes

Correct uput
Add interrupt masking otherwise we can take an IRQ while we are within a
usermem access with no valid stack. At that point we crapped a stack frame
somewhere in the wrong memory bank.