OPT Cache Predef_conforms in the current run.

And refer to this in Implicit search
OPT Avoid needless TypeRef allocation during erasure.

  - some.package.type need not be erased
  - erasing a no-args type ref with a trivial prefix is an identity,
     reuse the original TypeRef
OPT (?) this.toString rather than String.valueOf(this)
OPT TermSymbol name tests can use rawname

Avoiding the non-monomorphic name.
OPT support wrapped java.util.HashMap in perRunCaches.
OPT Use Java hashmap for in GenASM javaName caches
OPT (?) Use wrapped Java hashmap in backend ScalaPrimitives
OPT faster Definitions#isGetClass
  - check if it is a method symbol
  - avoid megamorphic, bridged call to Symbol#name
OPT move ArrayInstantiation extractor out of `typed1`.
OPT missing piece of Erasure TypeRef optimization.
OPT temporary hack to partially plug an FSC leak
OPT reduce number of calls to Tree#symbol
OPT second part of hack to plug memory leak
OPT (?) hand roll some more hashcodes rather than using productHashCode
OPT optimize TreeInfo#isMacroApplication.
OPT ClassInfoType and PackageClassInfoType are grounded

(Correct?)
OPT (?) try making Symbol#name bimorphic
OPT (?) break up mapOver to see as a peace offering to JIT
OPT (?) try to specialized Transformers under reflect internal

COPY/PASTE alert!

Rather than bouncing between transform and itransform.
OPT (?) direct internal tree traverser

No bouncing between traverse/itraverse.

Big Copy/Paste alert.

No speedup in my benchmark :( But lets see where this leads..