libsyntax: Remove last use of structural records in pipes compiler.
libsyntax: Explicit-self-ify pipes compiler.
libsyntax: Long lines.
auto merge of #4996 : luqmana/rust/no-rec-pipes, r=catamorphism

Removes the last use of structural records in the pipes extension and with that, libcore has no more structural records.
Also, explicit-self-ification.