Epic: Integrate changes in mspnf/zinc

[dwijnand]

• Build pipelining (also Build pipelining scala/scala-dev#643) Build pipelining support #744
  • changes to the InvalidationProfiler (not the synchronizeds) [545c917 (#744) ](545c917)
  • cancellation: Zinc users need access to nsc's reporter.cancelled = true (advance is sufficient)
• Referentially transparent (RT) builds
  • Map analysis relations paths in binary format too #782 allow paths to be mapped so that artifacts read from analyses match those on the compilation classpath
  • quickApi / provenance
    • extend existing Lookup api (which is already customizable) to include lookupAnalyzedClass Push lookupAnalyzedClass into Lookup #785
    • add provenance to AnalyzedClass Introduce "provenance" to AnalyzedClass #786
  • override
    ExternalHooks#hashClassPath to compute FileHash directly from the file names (nothing TODO, already available since Allow clients to override hashing classpath. #427)
• Virtual source files Add VirtualFile / VirtualFileRef #712
• Additional changes
  • SafeLazy concurreny issue Fix concurrency issue in SafeLazy #740
  • optimized UsedName's scopes Memory efficiency for used names collection and other Relations building #764 (postponed)
  • Map<String, Object extraHooks() + Hooks methods to set and retrieve specific hooks and callbacks (this was for expediency, replace with typed API additions
  • Make hashing childrenOfSealedClass stable Make hashing childrenOfSealedClass stable #788
• additional performance tickets (postponed)

original diff: https://github.com/sbt/zinc/compare/develop...mspnf:1.3.x-contrib?w=1 (formatted)

[dwijnand]

Done. The remaining additional changes will follow on (or not, as they're looked at 1 by 1).