MFC r308493, r308619: Update amd from am-utils 6.1.5 to 6.2.

Used extensively on my network over the past ten weeks.

Reviewed by: pfg, brooks
Suggested by: pfg
Obtained from: ftp://ftp.am-utils.org/pub/am-utils/
Relnotes: yes
Differential Revision: D8405

MFV r277814, r277868, r277869:
amd: Add extra check for NULL before deref.

MFV r277841:
Fix a clang 3.6.0 warning (from dim)

CID: 274421
Obtained from: NetBSD
MFC after: 4 days

MFV r277814, r277868, r277869:
amd: Add extra check for NULL before deref.

MFV r277841:
Fix a clang 3.6.0 warning (from dim)

CID: 274421
Obtained from: NetBSD
MFC after: 4 days