Delimited continuations in OCaml go to 3.12 and 64

[oleg@okmij.org]

The library delimcc implements multi-prompt delimited control operators
for byte- and native-code OCaml. The library now can be used with
OCaml 3.12.0, on x86_32 and x86_64 (aka amd64) platforms.

The byte-code part of the previous versions of delimcc could
already be used with OCaml 3.12 (although I didn't know that). Since
OCaml byte-code is portable, the byte-code delimcc should work on
any supported architecture. In this version, some adjustments have
been made to scAPI to make in more portable. It should be stressed
that there are _no_ distinct versions of the native-code delimcc, for
32- and 64-bit architectures. Rather, the same code (without any
64-bit--specific ifdefs) works on x86_32 and x86_64. Only
C code differs between byte-code and native-code versions of the
library; the OCaml code is shared, across the versions and the
architectures. The current version of delimcc probably works on other
architectures like arm, although I have no means of testing that.

The byte- and native-code versions of library has been tested on i386
Linux and FreeBSD platform and on amd64 Linux platform. The code is at

	http://okmij.org/ftp/continuations/caml-shift.tar.gz

I thank Jim Pryor for help with testing.