Setting up compiler support and several related additions to util/io

* Added the top-level interface project for communicating across scala versions within a jvm.
 * Added plugin project containing analysis compiler plugin
 * Added component compiler to build xsbt components against required version of Scala on the fly
 * Added interface to compiler that runs in the same version of Scala
 * Added frontend that compiles against a given version of Scala with or without analysis.

interface/src/main/java/xsbti/AnalysisCallback.java

@@ -0,0 +1,35 @@
+/* sbt -- Simple Build Tool
+ * Copyright 2008, 2009  Mark Harrah
+ */
+package xsbti;
+
+import java.io.File;
+
+public interface AnalysisCallback
+{
+	/** The names of classes that the analyzer should find subclasses of.*/
+	public String[] superclassNames();
+	/** Called when the the given superclass could not be found on the classpath by the compiler.*/
+	public void superclassNotFound(String superclassName);
+	/** Called before the source at the given location is processed. */
+	public void beginSource(File source);
+	/** Called when the a subclass of one of the classes given in <code>superclassNames</code> is
+	* discovered.*/
+	public void foundSubclass(File source, String subclassName, String superclassName, boolean isModule);
+	/** Called to indicate that the source file <code>source</code> depends on the source file
+	* <code>dependsOn</code>.*/
+	public void sourceDependency(File dependsOn, File source);
+	/** Called to indicate that the source file <code>source</code> depends on the jar
+	* <code>jar</code>.*/
+	public void jarDependency(File jar, File source);
+	/** Called to indicate that the source file <code>source</code> depends on the class file
+	* <code>clazz</code>.*/
+	public void classDependency(File clazz, File source);
+	/** Called to indicate that the source file <code>source</code> produces a class file at
+	* <code>module</code>.*/
+	public void generatedClass(File source, File module);
+	/** Called after the source at the given location has been processed. */
+	public void endSource(File sourcePath);
+	/** Called when a module with a public 'main' method with the right signature is found.*/
+	public void foundApplication(File source, String className);
+}

interface/src/main/java/xsbti/AnalysisCallbackContainer.java

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+/* sbt -- Simple Build Tool
+ * Copyright 2009  Mark Harrah
+ */
+package xsbti;
+
+/** Provides access to an AnalysisCallback.  This is used by the plugin to
+* get the callback to use.  The scalac Global instance it is passed must
+* implement this interface. */
+public interface AnalysisCallbackContainer
+{
+	public AnalysisCallback analysisCallback();
+}

interface/src/main/java/xsbti/F0.java

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+/* sbt -- Simple Build Tool
+ * Copyright 2009  Mark Harrah
+ */
+package xsbti;
+
+public interface F0<T>
+{
+	public T apply();
+}

interface/src/main/java/xsbti/Logger.java

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+/* sbt -- Simple Build Tool
+ * Copyright 2009  Mark Harrah
+ */
+package xsbti;
+
+public interface Logger
+{
+	public void error(F0<String> msg);
+	public void warn(F0<String> msg);
+	public void info(F0<String> msg);
+	public void debug(F0<String> msg);
+	public void trace(F0<Throwable> exception);
+}