Variable-sized register frames

[Leopold Toetsch]

Folks watching SVN checkins have already seen some patches floating by
with:
"Variable-sized reg frames" in the log head line.

The complete plan is now available at: http://perlcabal.org/~lt/VR.txt
There will be no visible impact on the surface of Parrot, all code will
continue to run, *except* code that uses deprecated register stack
opcodes from the file DEPRECATED.

The opcodes C<saveall> and C<restoreall> will be supported in the
future, but with a by far more efficient implementation. Currently each
of these opcodes comprises *eight* stack operation to copy 640 (32-bit
arch) bytes.
The reimplementation will just be one stack-like operation, to copy
exactly what is needed, which will be typically a lot less. This makes
all the over half-frame copy opcodes and such obsolete, so these will
be tossed RSN.

leo