Dtrace: add toupper()/tolower() and enhancements to lltostr().

Dtrace: add toupper()/tolower() and enhancements to lltostr().

Merge changes from illumos:

1451 DTrace needs toupper()/tolower() subroutines
1457 lltostr() D subroutine should take an optional base

This change bumps the DT_VERS_* number to 1.8.1 in
accordance to what is done in illumos.

The test suite we currently include is outdated and
doesnt support some updates in tst.subr.d which had to
be left out for now.

Illumos Revisions:	r13458 5e394d8db762
			r13459 c3454574dd1a

Reference:
https://www.illumos.org/issues/1451
https://www.illumos.org/issues/1457

Tested by:	Fabian Keil
Obtained from:	Illumos
MFC after:	1 month