signal::SigFlags should be enum instead of bitflags.

[chaosagent]

http://man7.org/linux/man-pages/man3/pthread_sigmask.3.html

SigFlags represents the how parameter of pthread_sigmask, which takes 3 mutually exclusive options, which should be represented by an enum. The SigFlags name is pretty confusing too, as the underlying value is an option, not a flag.

[chaosagent]

Fixing this would require some breaking changes, but I don't know what the policy on that is.

[kamalmarhubi]

Fixing this would require some breaking changes, but I don't know what the policy on that is.

A big part of the motivation for a changelog is to at least make it possible to see what has changed. Pre-1.0 we're fairly happy to make changes for API improvements. This is fixing the semantics of an API and should certainly be allowed, IMO.

[kamalmarhubi]

For more on this parameter: http://man7.org/linux/man-pages/man2/sigprocmask.2.html#DESCRIPTION

Certainly agree this should be an enum.

[fiveop]

#460 is merged, so this issue can be closed.