Split SETCC if VSELECT requires splitting too.

This patch is a rewrite of the original patch commited in r194542. Instead of
relying on the type legalizer to do the splitting for us, we now peform the
splitting ourselves in the DAG combiner. This is necessary for the case where
the vector mask is a legal type after promotion and still wouldn't require
splitting.

Patch by: Juergen Ributzka

NOTE: This is a candidate for the 3.4 branch.
SelectionDAG: Optimize expansion of vec_type = BITCAST scalar_type

The legalizer can now do this type of expansion for more
type combinations without loading and storing to and
from the stack.

NOTE: This is a candidate for the 3.4 branch.
R600: Implement TargetInstrInfo::isLegalToSplitMBBAt()

Splitting a basic block will create a new ALU clause, so we need to make
sure we aren't moving uses of registers that are local to their
current clause into a new one.

I had a test case for this, but unfortunately unrelated schedule changes
invalidated it, and I wasn't been able to come up with another one.

NOTE: This is a candidate for the 3.4 branch.
[PM] Switch analysis managers to be threaded through the run methods
rather than the constructors of passes.

This simplifies the APIs of passes significantly and removes an error
prone pattern where the *same* manager had to be given to every
different layer. With the new API the analysis managers themselves will
have to be cross connected with proxy analyses that allow a pass at one
layer to query for the analysis manager of another layer. The proxy will
both expose a handle to the other layer's manager and it will provide
the invalidation hooks to ensure things remain consistent across layers.
Finally, the outer-most analysis manager has to be passed to the run
method of the outer-most pass manager. The rest of the propagation is
automatic.

I've used SFINAE again to allow passes to completely disregard the
analysis manager if they don't need or want to care. This helps keep
simple things simple for users of the new pass manager.

Also, the system specifically supports passing a null pointer into the
outer-most run method if your pass pipeline neither needs nor wants to
deal with analyses. I find this of dubious utility as while some
*passes* don't care about analysis, I'm not sure there are any
real-world users of the pass manager itself that need to avoid even
creating an analysis manager. But it is easy to support, so there we go.

Finally I renamed the module proxy for the function analysis manager to
the more verbose but less confusing name of
FunctionAnalysisManagerModuleProxy. I hate this name, but I have no idea
what else to name these things. I'm expecting in the fullness of time to
potentially have the complete cross product of types at the proxy layer:

{Module,SCC,Function,Loop,Region}AnalysisManager{Module,SCC,Function,Loop,Region}Proxy

(except for XAnalysisManagerXProxy which doesn't make any sense)

This should make it somewhat easier to do the next phases which is to
build the upward proxy and get its invalidation correct, as well as to
make the invalidation within the Module -> Function mapping pass be more
fine grained so as to invalidate fewer fuction analyses.

After all of the proxy analyses are done and the invalidation working,
I'll finally be able to start working on the next two fun fronts: how to
adapt an existing pass to work in both the legacy pass world and the new
one, and building the SCC, Loop, and Region counterparts. Fun times!
Fix a typo where we were creating <def,kill> operands instead of
<def,dead> ones.

Add an assertion to make sure we catch this in the future.

Fixes <rdar://problem/15464559>.
[PM] Simplify how the SFINAE for AnalysisResultModel is applied by
factoring it out into the default template argument so clients don't
have to even think about it.
#include <AvailabilityMacros.h> if you want to use them.  This was causing us to skip
the code that should have set thread names on Mac OS X.

<rdar://problem/15517264>
The cmpxchg16 feature has been renamed cx16.
Comment parsing tests: XML schema: actually run the valid-function-10.xml test

It was there all the time, but I missed adding a RUN line for it.
SLP Vectorizer: Extract cost will only be added once even if the scalar has multiple external uses.