test: increase timeouts on ARM

This commit introduces platform-specific test timeouts for the ARM
architectures. ARMv6 is notoriously slow so gets very large timeouts on
both the timeout value for each test, as well as certain problematic
individual tests. ARMv7 and ARMv8 also get slightly increased headroom.

PR-URL: https://github.com/iojs/io.js/pull/1366
Fixes: https://github.com/iojs/io.js/issues/1343


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>