build: add basic arm64 support

This commit adds basic arm64 support to the build.  Building the bundled
openssl is disabled pending an upgrade to openssl 1.2, the currently
bundled version has some hand-rolled assembly that is 32 bits only.

PR-URL: https://github.com/iojs/io.js/pull/1028


Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Rod Vagg <rod@vagg.org>