Refine MemRegions for blocks. Add a new region called

'BlockDataRegion' to distinguish between the code associated with a
block (which is represented by 'BlockTextRegion') and an instance of a
block, which includes both code and data.  'BlockDataRegion' has an
associated LocationContext, which can be used to eventually model the
lifetime of a block object once LocationContexts can represent scopes
(and iterations around a loop, etc.).

llvm-svn: 89900