x86-64: Integrate Paul Khuong's interleaved raw slot feature.

with significant amounts of conditionalization
and the new implementation of EQUALP and other fixes by me.
Fix some warnings from Darwin C compiler
Some improvements to the low-level debugger.

- fix printing of UCS4 strings
- make "p *A-SYMBOL*" work if *A-SYMBOL* has a UCS4 name
- generate 'classoid.h' from Genesis, and print instances
  with their classoid's name
Refactor b6ed0e20d468099b62d27095db7d18f76d8886d2

The description of the aforementioned commit wasn't quite
right - it meant "no defstruct-description".
This diff looks better with whitespace ignored.