Add a simple procdesc(4) man page describing "options PROCDESC" and the
high-level facility, supplementing pdfork(2) and friends.  Update capsicum.4
to xref.

Suggested by:	sbruno
MFC after:	3 days
Xref capsicum(4) and procdesc(4) from pdfork(2).

Suggested by:	sbruno
MFC after:	3 days
ql_minidump() should be performed only by port 0.

Submitted by: David C Somayajulu
Reduce diff against stable/9 slightly.