Remove dead option.
Add a bit of a hack to deal with a failing testcase on darwin10 bots.

We currently emit an error message when you try to use thread local
storage on targets that don't support it and testing C++11 thread
locals will trip this. We don't want to xfail the test for all darwin
hosts so add a quick hack to check for darwin10 and disable the
test based on that. Only checking darwin10 because anything earlier
is really old and I don't have a list of what other hosts don't
support tls handy.

Alternate suggestions welcome!
tests: Fix 'instruction does not dominate all its uses' error

The LLVM-IR of this test case was apperently incorrect.
Remove unneeded RegionSimplify pass.

We now support regions with multiple entries and multiple exits natively.
Regions are not needed to be simplified to single entry and single exit.

We need to XFAIL two test cases as this change increases the scop coverage
and uncoveres two failures in the independent blocks pass. The first failure
will be fixed in a subsequent commit, the second one is in the non-default
-polly-codegen-scev mode and still needs to be fixed.

Contributed-by: Star Tan <tanmx_star@yeah.net>
IndependentBlocks: We can only reconstruct PHI nodes that are within the ScoP

In the classical (non -polly-codegen-scev) mode, we assume that we can always
recreate PHI nodes during code generation. This is not true. We can only
reconstruct them from the polyhedral information, in case the entire loop of the
PHI node is part of the SCoP and consequently the PHI node was translated in
the polyhedral description.