Lazy bingding for region-store manager.

* Now Bind() methods take and return GRState* because binding could
  also alter GDM.
* No variables are initialized except those declared with initial
  values.
* failed C test cases are due to bugs in RemoveDeadBindings(),
which removes constraints that is still alive. This will be fixed in later
patch.
* default value of array and struct regions will be implemented in later patch.

llvm-svn: 61274