task execution interruptible using ctrl+c. fixes #228,#229

- interrupts task execution only
- no further tasks scheduled
- existing tasks interrupted
- a task must terminate any other started threads when interrupted
- set cancelable to true to enable
- currently, 'run' properly terminates if the application properly
   terminates when interrupted
- 'console' does not, 'test' depends on the test framework

- also bundled: set connectInput to true to connect standard input to forked run

util/collection/Signal.scala

@@ -0,0 +1,43 @@
+package sbt
+
+object Signals
+{
+	def withHandler[T](handler: () => Unit)(action: () => T): T =
+	{
+		val result = 
+			try
+			{
+				val signals = new Signals0
+				signals.withHandler(handler)(action)
+			}
+			catch { case e: LinkageError => Right(action()) }
+
+		result match {
+			case Left(e) => throw e
+			case Right(v) => v
+		}
+	}
+}
+
+// Must only be referenced using a
+//   try { } catch { case e: LinkageError => ... }
+// block to 
+private final class Signals0
+{
+	// returns a LinkageError in `action` as Left(t) in order to avoid it being
+	// incorrectly swallowed as missing Signal/SignalHandler
+	def withHandler[T](handler: () => Unit)(action: () => T): Either[Throwable, T] =
+	{
+			import sun.misc.{Signal,SignalHandler}
+		val intSignal = new Signal("INT")
+		val newHandler = new SignalHandler {
+			def handle(sig: Signal) { handler() }
+		}	
+
+		val oldHandler = Signal.handle(intSignal, newHandler)
+
+		try Right(action())
+		catch { case e: LinkageError => Left(e) }
+		finally Signal.handle(intSignal, oldHandler)
+	}
+}

util/process/Process.scala

@@ -166,6 +166,8 @@ trait ProcessBuilder extends SourcePartialBuilder with SinkPartialBuilder
 	* The newly started process reads from standard input of the current process if `connectInput` is true.*/
 	def run(log: ProcessLogger, connectInput: Boolean): Process
 
+	def runBuffered(log: ProcessLogger, connectInput: Boolean): Process
+
 	/** Constructs a command that runs this command first and then `other` if this command succeeds.*/
 	def #&& (other: ProcessBuilder): ProcessBuilder
 	/** Constructs a command that runs this command first and then `other` if this command does not succeed.*/

util/process/ProcessImpl.scala

@@ -159,10 +159,10 @@ private abstract class AbstractProcessBuilder extends ProcessBuilder with SinkPa
 
 	def ! = run(false).exitValue()
 	def !< = run(true).exitValue()
-	def !(log: ProcessLogger) = runBuffered(log, false)
-	def !<(log: ProcessLogger) = runBuffered(log, true)
-	private[this] def runBuffered(log: ProcessLogger, connectInput: Boolean) =
-		log.buffer {  run(log, connectInput).exitValue() }
+	def !(log: ProcessLogger) = runBuffered(log, false).exitValue()
+	def !<(log: ProcessLogger) = runBuffered(log, true).exitValue()
+	def runBuffered(log: ProcessLogger, connectInput: Boolean) =
+		log.buffer {  run(log, connectInput) }
 	def !(io: ProcessIO) = run(io).exitValue()
 
 	def canPipeTo = false