Make TempScopInfo a RegionPass

This modifies the order in which Polly passes are executed.

Assuming a function has two scops (A and B), the order before was:

FunctionPassManager
  ScopDetection
  IndependentBlocks
  TempScopInfo for A and B
  RegionPassManager
    ScopInfo for A
    DependenceInfo for A
    IslScheduleOptimizer for A
    IslAstInfo for A
    CodeGeneration for A
    ScopInfo for B
    DependenceInfo for B
    IslScheduleOptimizer for B
    IslAstInfo for B
    CodeGeneration for B

After this patch:

FunctionPassManager
  ScopDetection
  IndependentBlocks
  RegionPassManager
    TempScopInfo for A
    ScopInfo for A
    DependenceInfo for A
    IslScheduleOptimizer for A
    IslAstInfo for A
    CodeGeneration for A
    TempScopInfo for B
    ScopInfo for B
    DependenceInfo for B
    IslScheduleOptimizer for B
    IslAstInfo for B
    CodeGeneration for B

TempScopInfo for B might store information and references to the IR
that CodeGeneration for A might modify. Changing the order ensures that
the IR is not modified from the analysis of a region until code
generation.

Reviewers: grosser

Differential Revision: http://reviews.llvm.org/D12014

llvm-svn: 245091