Remove AnalysisCallback.{beginSource, endSource} methods.

As pointed out by @harrah in #705, both beginSource and endSource are
not used in sbt internally for anything meaningful.

We've discussed an option of deprecating those methods but since they
are not doing anything meaningful Mark prefers to have compile-time
error in case somebody implements or calls those methods. I agree with
that hence removal.

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

@@ -7,8 +7,6 @@ import java.io.File;
 
 public interface AnalysisCallback
 {
-	/** Called before the source at the given location is processed. */
-	public void beginSource(File source);
 	/** Called to indicate that the source file <code>source</code> depends on the source file
 	* <code>dependsOn</code>.  Note that only source files included in the current compilation will
 	* passed to this method.  Dependencies on classes generated by sources not in the current compilation will
@@ -24,8 +22,6 @@ public interface AnalysisCallback
 	/** Called to indicate that the source file <code>source</code> produces a class file at
 	* <code>module</code> contain class <code>name</code>.*/
 	public void generatedClass(File source, File module, String name);
-	/** Called after the source at the given location has been processed. */
-	public void endSource(File sourcePath);
 	/** Called when the public API of a source file is extracted. */
 	public void api(File sourceFile, xsbti.api.SourceAPI source);
 	/** Provides problems discovered during compilation.  These may be reported (logged) or unreported.