Add new interface to add ability to get/set signal mask of a tracee.
It has been inspired by Linux PTRACE_GETSIGMASK and PTRACE_SETSIGMASK, but
adapted for NetBSD API.
This interface is used for checkpointing software to set/restore context
of a process including signal mask like criu or just to track this property
in reverse-execution software like Record and Replay Framework (rr).
Add new ATF tests for this interface
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getsigmask1:
Verify that plain PT_SET_SIGMASK can be called
getsigmask2:
Verify that PT_SET_SIGMASK reports correct mask from tracee
setsigmask1:
Verify that plain PT_SET_SIGMASK can be called with empty mask
setsigmask2:
Verify that sigmask is preserved between PT_GET_SIGMASK and
PT_SET_SIGMASK
setsigmask3:
Verify that sigmask is preserved between PT_GET_SIGMASK, process
resumed and PT_SET_SIGMASK
setsigmask4:
Verify that new sigmask is visible in tracee
Kernel ABI bump delayed as there are more interfaces to come in ptrace(2).
Sponsored by <The NetBSD Foundation>
61aff29627