parallel_map crashes on computers with slow temp folder

[alejoforero]

parallel_map runs into frequent supposed "syntax" errors that crashes the program. Changing the sleep time in line 348 from 50 to e.g. 500 solves this problem. This is important for legacy servers which, while having slow drives for the temporary files folder, still have many cores that are useful to speed up simulations.

I propose adding a [sleep(integer 50)] option in the syntax, with default 50 as is now. Should I do a pull request?

Stata 17, MP4.
Windows Server 2019.