xsbti.Position: Also add {start,end}{Line,Column}

Positions in the Language Server Protocol and Build Server Protocol are
line/column-based instead of offset-based, so this is more convenient.
Computing the line/column from the offset is possible but requires
reading the source file.

Author: smarter

src/main/java/xsbti/Position.java

@@ -22,4 +22,8 @@ public interface Position
 	// Default values to avoid breaking binary compatibility
 	default Optional<Integer> startOffset() { return Optional.empty(); }
 	default Optional<Integer> endOffset() { return Optional.empty(); }
+	default Optional<Integer> startLine() { return Optional.empty(); }
+	default Optional<Integer> startColumn() { return Optional.empty(); }
+	default Optional<Integer> endLine() { return Optional.empty(); }
+	default Optional<Integer> endColumn() { return Optional.empty(); }
 }