Added a Materializer class that contains
information about each variable that needs to
be materialized for an expression to work.  The
next step is to migrate all materialization code
from ClangExpressionDeclMap to Materializer, and
to use it for variable materialization.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@179245 91177308-0d34-0410-b5e6-96231b3b80d8