[MIT-Scheme-devel] arm64 support

[Taylor R Campbell]

I merged my branch with support for aarch64[*] into master.  If you
want to try it, do:

# on an x86 machine with an existing >=10.1.9
./Setup.sh
./configure --enable-cross-compiling --enable-native-code=aarch64le
make cross-host

# transplant the source tree onto an aarch64 (little-endian) machine
# like rpi3 or pinebook
make cross-target
make check

Let me know if anything works!

(Open-coded floating-point arithmetic is currently disabled because I
haven't tested it enough but if you're brave you can do

(set! compiler:open-code-floating-point-arithmetic? #t)

when compiling your code.)


[*] `AArch64' is the formal name for the 64-bit ARM CPU instruction
    set which is also used by vendors Cavium whose hardware is
    emphatically not `ARM' hardware.  I read it as `AArgh64' instead
    but the world has settled on the unpronounceable aarch64 as the
    name for the instruction set, so here we are.