cl/cldebug: keep a type and its non-member fncs in the same namespace

See Herb Sutter: C++ Coding Standards (rule #104) for details.
sl/fixed_point: use polymorphism to represent insns
sl/fixed_point_rewrite: a new home for StateRewriter
sl/fixed_point_rewrite: use API based GenericInsn
sl/fixed_point_rewrite: implement move of loop-closing edges
sl/fixed_point_rewrite: provide AnnotatedInsn API [not tested]
sl/fixed_point_rewrite: require TextInsn to be annotated [not tested]
sl/fixed_point: use GenericVar in removeDeadCode()