Please add documentation on the .goto. pragma to Nim manual

[yuanweixin]

Summary

Please add documentation on the currently undocumented .goto. pragma to nim manual.

Description

I have been going through some code and came across the undocumented .goto. pragma. Initially I thought maybe it is related to (e.g. predecessor of) the computedGoto pragma, but it appears to be a different thing.

Example code where it is used

Did some googling and found a forum post where it is mentioned.

Relevant forum thread

And apparently it is a feature.

Araq:
This is not a hack btw and we should document it. It's a terrific design: We transform a control flow dependency into a data dependency so that all analysis algorithms that rely on structured control flow simply continue to work.

Please add doc to the nim manual so it is clear what .goto. can be used for. Thanks!