examples/ramutex/orig.da: fix legacy message syntax.
incgen: fix some names in queries not mangled.

* da/compiler/incgen.py(IncInterfaceGenerator): inherit from
   PatternComprehensionGenerator for more code reuse.

* da/compiler/pygen.py(PatternComprehensionGenerator.visit_FreePattern):
  don't assume we know anything about names, do a proper visit.