DTrace: re-merge remainder of r249367 (original from Illumos).

DTrace: re-merge remainder of r249367 (original from Illumos).

Bring back some important fixes from Illumos:

3022 DTrace: keys should not affect the sort order when sorting by value
3023 it should be possible to dereference dynamic variables
3024 D integer narrowing needs some work

We particularly avoid the LD_NOLAZYLOAD changes that Illumos made
as those don't apply to FreeBSD and were causing problems in
interactive mode.

Illumos Revision:	13758:23432da34147

Reference:

https://www.illumos.org/issues/3022
https://www.illumos.org/issues/3023
https://www.illumos.org/issues/3024

MFC after:	1 month
Tested by:	markj