K 10
svn:author
V 4
ngie
K 8
svn:date
V 27
2017-03-21T19:02:17.583803Z
K 7
svn:log
V 564
kvm_geterr: handle `kd` == NULL in a deterministic/graceful manner

Return a NUL string instead of just working by accident with kvm_geterr(3)
when MALLOC_PRODUCTION is disabled (I didn't confirm the MALLOC_PRODUCTION
being enabled path).

Document the new explicit return behavior for kvm_geterr(3), as well
as the previous implicit behavior, i.e., the buffer attached to
returned via kvm_geterr(3) would be empty if a previous error hadn't been
stored in `kd`.

Differential Revision:	D10022
MFC after:	1 week
Reviewed by:	vangyzen
Sponsored by:	Dell EMC Isilon

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