Invokedynamic backed lambdas

  - Replace `<<load args>>; new anon$fun; <init>`
         by `<<load args>>; invokedynamic`
  - adjust to flipped captured/lambda parameter group order
    in the body of the old-school anonymous function lambda
  - Don't emit the anonymous class at all

    % export J8_COMPAT=/code/scala-java8-compat/target/scala-2.10/scala-java8-compat_2.10-0.1.0-SNAPSHOT.jar
    % qbin/scalac -Ybackend:GenBCode -Ydelambdafy:method -target:jvm-1.8 sandbox/test.scala
    % qbin/scala -classpath .:${J8_COMPAT} -nc Lambda
Disable -Ydelambdafy:method for specialized FunctionN
Add scala-java8-compat to scala-library.jar
Force run/t7974.scala to use GenASM
Support specialized method-handle based lambdas
WIP GenASM closure elimination