Move fields into local variables.
Move fields into local variables.

The method `areTrivialParams` is assumed to be used at most once
per MethodType object, so there is no need to keep the arrays as
fields. Instead, we can turn them into local method variables.

- Since the main loop goes parameter by parameter, we need not
  to keep the ContainsCollector objects, only the types.

- We unroll the main loop, so that we first check the `.isTrivial`
  method of each type, and only afterwards check with anyContains.

lrytz/scala,lrytz/scala,martijnhoekstra/scala,scala/scala,martijnhoekstra/scala,martijnhoekstra/scala,scala/scala,lrytz/scala,scala/scala,scala/scala,lrytz/scala,scala/scala,martijnhoekstra/scala,lrytz/scala,lrytz/scala,martijnhoekstra/scala,scala/scala,martijnhoekstra/scala