Static analyzer:

- Added a new 'node builder' class called GRStmtNodeBuilderRef (name may
  change). This is essentially a smart reference to a GRStmtNodeBuilder object
  that keeps track of the current context (predecessor node, GRExprEngine
  object, etc.) The idea is to gradually simplify the interface between
  GRExprEngine and GRTransferFuncs using this new builder (i.e., passing 1
  argument instead of 5). It also handles some of the "auto-transition" for node
  creation, simplifying some of the logic in GRExprEngine itself.

- Used GRStmtBuilderRef to replace GRTransferFuncs::EvalStore with
  GRTransferFuncs::EvalBind. The new EvalBind method will be used at any
  arbitrary places where a binding between a location and value takes place.
  Moreover, GRTransferFuncs no longer has the responsibility to request
  StoreManager to do the binding; this is now in GRExprEngine::EvalBind. All
  GRTransferFuncs::EvalBind does is checker-specific logic (which can be a
  no-op).

llvm-svn: 64525