MFV r316863: 3871 fix issues introduced by 3604

MFV r316863: 3871 fix issues introduced by 3604

illumos/illumos-gate@de05b58863498b10283637eb9ac85e92fe85150e
https://github.com/illumos/illumos-gate/commit/de05b58863498b10283637eb9ac85e92fe85150e

https://www.illumos.org/issues/3871
  GCC 4.5.3 on Gentoo Linux did not like a few of the changes made in the issue
  3604 patch. It printed an error and a couple of warnings:
  ../../cmd/zdb/zdb.c: In function 'dump_bpobj':
  ../../cmd/zdb/zdb.c:1257:3: error: 'for' loop initial declarations are only
  allowed in C99 mode
  ../../cmd/zdb/zdb.c:1257:3: note: use option -std=c99 or -std=gnu99 to compile
  your code
  ../../cmd/zdb/zdb.c: In function 'dump_deadlist':
  ../../cmd/zdb/zdb.c:1323:8: warning: too many arguments for format
  ../../cmd/zdb/zdb.c:1323:8: warning: too many arguments for format

Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Richard Yao <ryao@gentoo.org>

MFC after:	3 weeks