Add new manual pages:

• c++filt(1)
• xo_open_marker(3)
• xo_set_version(3)
• ds1307(4)
• dtrace-io(4)
• dtrace-ip(4)
• dtrace-proc(4)
• dtrace-sched(4)
• dtrace-tcp(4)
• dtrace-udp(4)
• pmcstudy(8)
• sntp(8)

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