check 2.0 for OTP-18.0 deprecations

Based on errors from 1.6.x branch, these may be worth checking:

A few more warnings appear as expected, crypto & time stuff.

erlang:now/0 as we know
calendar:local_time_to_universal_time/1 -> calendar:local_time_to_universal_time_dst/1
crypto:sha_mac/2 -> crypto:hmac/3
crypto:sha/1 -> crypto:hash/2
crypto:md5_init/0 -> crypto:hash_init/1
crypto:md5_update/0 -> crypto:hash_update/1
crypto:md5_final/0 -> crypto:hash_final/1