Add stub clean up block for exceptions

This is going to be used to un-root our GCed values when recovering from
an exception. Right now it should be a no-op

- Generate stub clean up block that immediately resumes exception
  handling

- Switch from using "call" to "invoke"  for instructions that can throw
  exceptions
Scala 2.11.0 preparation

This is still a Scala 2.10.4 project but has fixes to work better with
the upcoming 2.11.0 release:

- Fix compile errors due to protected classes now being hidden outside
  their package

- Fix warnings produced by -Xlint -Ywarn-unused except for a spurious
  warning related to IntCounter

- Fix warnings products by -Ywarn-unused-import except for imports of
  "io.llambda" which are at the beginning of every scala file to ensure
  "llambda" is available

- Small typo and unit test fixes for issues encountered during the
  above