Backport the fix from the upstream and add our testcase.
Backported cset:
commit 997a979bf5e2f75ab88781d9d3fd22dddc1fc21f
Author: Manuel Ung <mung@fb.com>
Date:   Thu Feb 15 08:38:12 2018 -0800

    Fix crashes in autoincrement code paths

    Summary:
    There are two issues related to autoincrement that can lead to crashes:

    1. The max value for double/float type for autoincrement was not implemented in MyRocks, and can lead to assertions. The fix is to add them in.
    2. If we try to set auto_increment via alter table on a table without an auto_increment column defined, we segfault because there is no index from which to read the last value. The fix is to perform a check to see if autoincrement exists before reading from index (similar to code ha_rocksdb::open).

    Fixes https://github.com/facebook/mysql-5.6/issues/792
    Closes https://github.com/facebook/mysql-5.6/pull/794

    Differential Revision: D6995096

    Pulled By: lth

    fbshipit-source-id: 1130ce1