=pro sbt-0.13.2-M2 with name hashing

* take advantage of latest incremental compiler improvements

One data point. Compiling akka-actor after adding a new method in the Actor trait.

sbt 0.13.1:

    akka-actor > compile
    [info] Formatting 1 Scala source {file:/Users/patrik/tmp/akka/}akka-actor(compile) ...
    [info] Compiling 1 Scala source to /Users/patrik/tmp/akka/akka-actor/target/classes...
    [info] Compiling 113 Scala sources and 21 Java sources to /Users/patrik/tmp/akka/akka-actor/target/classes...
    [success] Total time: 12 s, completed Mar 7, 2014 9:41:49 AM

sbt 0.13.2-M2:

    akka-actor > compile
    [info] Formatting 1 Scala source {file:/Users/patrik/dev/akka/}akka-actor(compile) ...
    [info] Compiling 1 Scala source to /Users/patrik/dev/akka/akka-actor/target/classes...
    [info] Compiling 46 Scala sources and 4 Java sources to /Users/patrik/dev/akka/akka-actor/target/classes...
    [success] Total time: 8 s, completed Mar 7, 2014 9:40:52 AM