Hello, I was wondering if there was a pragma to restrict the use of some procedures to the main thread.
The use case I have is that I did some bindings of the glibc DNS resolution procedures in the [resolv](https://github.com/mildred/resolv.nim/) nimble, and I believe that the glibc procedures are not thread safe. As such, I would like to restrict the nim procedures to a single thread only. There is the `{.gcsafe.}` pragma that kind of does the opposite, but it's tied to the garbage collector that's going away. And I want to specifically mark a procedure not thread safe. Perhaps if that does not exists, it could be a nice small addition.
