Correct the insertion of the rootmapfile entry in the already seen forward decls. (ROOT-6063 and 6141).

- add only for clang compiler flag -Wno-unused-funciton to suppress the warning

(Thanks Bertrand to have seen it :-) )

To provide an example for the fix/change for ROOT-748 just committed.

To get the same behaviour as in Tree::Process.
The TSelector::fStatus of all non-aborted workers are added.

The 'simple' (TRadialGradient::kSimple) implemented with OpenGL.

Collect the already returned information to return 0 in case of success, -1 in the
case at leat one node did not manage to set the wanted version

“update to latest Vc 0.7 branch”

Vc cmake code needs to do some extra/different calls when inside ROOT.
In order to easily sync with upstream the Vc_INSIDE_ROOT variable is
used.

Signed-off-by: Matthias Kretz <kretz@kde.org>