incgen: name must be mangled in entire inc module.

Since all parameters are in inc module global scope, these names must be
consistently mangled across entire inc module, including both queries
and updates.

* da/compiler/dast.py(NamedVar.is_assigned_in): new method.

* da/compiler/incgen.py:

  -(gen_query_stub): new function, refactored from `gen_inc_module`.

  -(gen_update_stub): make sure to mangle the nameobj itself.

  -(gen_inc_module): refactored to use `gen_query_stub`.

  -(EventExtractor): dedup events.

  -(IncInterfaceGenerator.visit_AttributeExpr): properly handle
   "self.XXX" names, by finding and visiting the corresponding name
   object.

* da/compiler/parser.py(Parser): don't generate local arguments for
  'setup()': setup's arguments are process arguments; don't add
  'setup()' to process.methods, instead set process.setup.

* da/compiler/pygen.py(PythonGenerator): generate 'setup()' before
  'main()', right after '__init__()'; use process arguments as setup
  arguments.