mod_debug_traceback: Remove direct POSIX signal handling, require Prosody 0.12+
Hooking an event is safer than directly hooking signals
For context see Prosody trunk rev 69faf3552d52
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summary: Remote Roster Management
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Introduction
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This module adds support for [XEP-0321: Remote Roster Management] which
is commonly used to allow components such as transports to modify the
rosters of local users.