missing(?) imports, fix emacs syntax highlighting

While trying to build sbt without sbt, I got compile errors claiming that
util.Random would not be a member of util. The added import statements fixed
this.

The inserted spaces in the comments in project/Sbt.scala are a work around in a
bug in emacs scala syntax highlighting.

compile/api/HashAPI.scala

@@ -3,6 +3,7 @@
  */
 package xsbt.api
 
+import scala.util
 import xsbti.api._
 import util.MurmurHash
 import TagTypeVariables.TypeVars