Illumos #3006

3006 VERIFY[S,U,P] and ASSERT[S,U,P] frequently check if first
     argument is zero

Reviewed by Matt Ahrens <matthew.ahrens@delphix.com>
Reviewed by George Wilson <george.wilson@delphix.com>
Approved by Eric Schrock <eric.schrock@delphix.com>

References:
  illumos/illumos-gate@fb09f5aad4
  https://illumos.org/issues/3006

Requires:
  zfsonlinux/spl@1c6d149feb

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1509

include/sys/zfs_context.h

@@ -72,7 +72,6 @@
 #define	_SYS_RWLOCK_H
 #define	_SYS_CONDVAR_H
 #define	_SYS_SYSTM_H
-#define	_SYS_DEBUG_H
 #define	_SYS_T_LOCK_H
 #define	_SYS_VNODE_H
 #define	_SYS_VFS_H
@@ -112,6 +111,7 @@
 #include <sys/u8_textprep.h>
 #include <sys/fm/fs/zfs.h>
 #include <sys/sunddi.h>
+#include <sys/debug.h>
 
 /*
  * Stack