[Polly][NewPM][WIP] Add a ScopPassManager

This patch adds both a ScopAnalysisManager and a ScopPassManager.

The ScopAnalysisManager is itself a Function-Analysis, and manages
analyses on Scops. The ScopPassManager takes care of building Scop pass
pipelines.

This patch is marked WIP because I've left two FIXMEs which I need to
think about some more. Both of these deal with invalidation:

Deferred invalidation is currently not implemented. Deferred
invalidation deals with analyses which cache references to other
analysis results. If these results are invalidated, invalidation needs
to be propagated into the caching analyses.
The ScopPassManager as implemented assumes that ScopPasses do not affect
other Scops in any way. There has been some discussion about this on
other patch threads, however it makes sense to reiterate this for this
specific patch.
I'm uploading this patch even though it's incomplete to encourage
discussion and give you an impression of how this is going to work.

Differential Revision: https://reviews.llvm.org/D33192

llvm-svn: 303062