- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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The test suite we currently include is outdated and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

Update vendor/illumos/dist to pre libzfs_core state (dtrace and ctf part)
illumos-gate revision 13742:b6bbdd77139c

Obtained from: ssh://anonhg@hg.illumos.org/illumos-gate