Optimize generic signatures utility method `dotCleanup`
Avoid needless Name creation

 - Don't create names just to perform prefix/suffix checks
 - Don't create names, decode, *and* intern strings in ICode
Optimization in Uncurry

Only perform HashMap lookup of a tree until after checking more
cheaply if it refers to a symbol with by-name parameter type.
Avoid work in GenICode#run when inactive.

scalaPrimitives.init() represented 1% of a small (1s)
compilation run.
Merge pull request #3449 from retronym/topic/opt11

Another grab bag of compiler optimizations