exp/ssa: fixed bug (typo) in findPromotedField.
By appending to the wrong (always empty) list, only the last
anonymous field was being considered for promotion.
Also:
- eliminated "function-local NamedTypes" TODO; nothing to do.
- fixed Function.DumpTo: printing of anon receivers was "( T)",
now "(T)"; extracted writeSignature into own function.
- eliminated blockNames function;
thanks to BasicBlock.String, "%s" of []*BasicBlock is fine.
- extracted buildReferrers into own function.
exp/ssa can now build its own transitive closure.
R=gri
CC=golang-dev
https://golang.org/cl/
7384054