commit de9c683fc7977c51e00e63687fb764b9cbe2c7e6
author Joan Touzet <joant@atypical.net> Mon Jan 13 12:57:51 2020 -0500
committer Paul J. Davis <paul.joseph.davis@gmail.com> Mon Jan 13 16:29:40 2020 -0600
tree 4783c3ebba9fa82ea849660e076bd60eb03eaaaa
parent efb374a6493c4220333a201b649649736ddcc528

Eliminate multiple compiler warnings

We now only support OTP 20+, with 19 at a stretch. erlang:now/0
was deprecated in OTP 18, so we can now suppress these warnings:

```
/home/joant/couchdb/src/dreyfus/src/dreyfus_index_updater.erl:62: Warning: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
/home/joant/couchdb/src/dreyfus/src/dreyfus_index_updater.erl:83: Warning: erlang:now/0: Deprecated BIF. See the "Time and Time Correction in Erlang" chapter of the ERTS User's Guide for more information.
```

Also, some unused variables were removed:

```
/home/joant/couchdb/src/couch/src/couch_bt_engine.erl:997: Warning: variable 'NewSeq' is unused
/home/joant/couchdb/src/mem3/src/mem3_rep.erl:752: Warning: variable 'TMap' is unused
/home/joant/couchdb/src/dreyfus/src/dreyfus_httpd.erl:76: Warning: variable 'LimitValue' is unused
/home/joant/couchdb/src/dreyfus/src/dreyfus_util.erl:345: Warning: variable 'Db' is unused
```

PRs to follow in ets_lru, hyper, ibrowse to track the rest of `erlang:now/0`
deprecations.