www 66.html aarch64->arm64

[Oliver Marugg]

Hi

Found another a small addition to www 66.html, pls. change platform name 
from aarch64 to arm64 . -oliver

as the base system compiler.
<li>The powerpc architecture is now provided with
<a href="https://man.openbsd.org/clang.1";>clang(1)</a>, in
- addition to aarch64, amd64, armv7, i386, mips64el, sparc64.
+ addition to arm64, amd64, armv7, i386, mips64el, sparc64.