the custom scalac Reporter now delegates to an instance of
an sbt interface called xsbti.Reporter
handling compilation logging is now mainly done on the sbt-side of the
compiler interface
the xsbti.Reporter interface provides access to richer information
about errors and warnings, including source file, line, and offset
xsbti.Reporter can be implemented by users to get access to
detailed information without needing to parse the logging output
the CompileFailed exception that is thrown when compilation fails now
includes an array of the problems, providing detailed
error and warning information that can, for example, be consumed
by doing a mapFailure on 'compile' and using 'Compile.allProblems'
Mark Harrah