It replaces previous TRAP_HWWPT and is designed to be used for debug
register traps (both watchpoints and breakpoints).
TRAP_HWWPT wasn't documented in siginfo(2) neither noted in doc/CHANGES -
- document it and add new entry in CHANGES. This move is a step towards
switch the watchpoint ptrace(2) api to PT_*DBREGS.
This code was introduced recently and has no impact on stable releases.
Sponsored by <The NetBSD Foundation>
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