9e088e4164
This patch: * removes the "default" opt level, on the basis that it has no definition and is referred to nowhere in the compiler. * renames the "fastest" level to "none". The resulting set of transformations is unchanged. * renames the "best" level to "speed_and_size". The resulting set of transformations is unchanged. * adds a new level, "speed". This is the same as "speed_and_size" except that it omits transformations aimed only at reducing code size. Currently it omits only the insn shrinking pass.
This crate contains the metaprogram used by cranelift-codegen. It's not useful on its own.