WL#1092: Parallel load data infile and bulk insert

Affects: Server-7.1   —   Status: Un-Assigned   —   Priority: Medium

We shall make MySQL to be able use multiple CPUs for bulk inserts, "LOAD DATA
INFILE", Alter table to get better performance on larger boxes.

Now we have some partial solution but it works only for MyISAM and only for
complete index rebuilds.

We might have special option something like  ALTER  PARALLEL=4  TABLE ...
to be able to mannage how many resources the long statement would consume.

Note we need special care for auto_increment values if we load data in the parallel.

This task was inspired by attempt to create rows table on 16CPU
32G box.