`ccall` macros for controlling SIGINT handling

[ninjaaron]

@tkf

If you are wrapping ccall, another thing you can do is to wrap it with disable_sigint https://docs.julialang.org/en/v1.2-dev/base/c/#Base.disable_sigint so that you don’t have to worry when calling the C functions that may not be interrupt safe.

Good idea. (… two minutes later…) On the other hand, what about calls that block for a while and are interrupt safe? Is that really something that should be automatic? maybe it should be a different macro? maybe an optional flag?