Added preliminary support for CompoundLiterals in the static analyzer:

- GRExprEngine::VisitCompoundLiteral...
   (1) visits the initializer list (generating ExplodedNodes)
   (2) creates a CompoundMemRegion for the literal
   (3) creates a new state with the bound literal values using
       GRStateManager::BindCompoundLiteral

- GRStateManager::BindCompoundLiteral simply calls 
  StoreManager::BindCompoundLiteral to get a new store and returns a persistent
  GRState with that store.

- BasicStore::BindCompoundLiteral simply returns the same store, as it
  doesn't handle field sensitivity
  
- RegionStore::BindCompoundLiteral currently fires an assert (pending discussion
  of how to best implement mappings for CompoundLiteralRegion).

llvm-svn: 58277