Make some logging.

foo.patch

diff --git a/org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/Launcher.java b/org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/Launcher.java
index b543a73..2e79066 100644
--- a/org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/Launcher.java
+++ b/org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/Launcher.java
@@ -11,6 +11,8 @@
  ******************************************************************************/
 package org.eclipse.lsp4j.jsonrpc;
 
+import java.io.File;
+import java.io.FileNotFoundException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.PrintWriter;
@@ -239,6 +241,17 @@ public interface Launcher<T> {
 		
 		public Builder<T> setLocalService(Object localService) {
 			this.localServices = Collections.singletonList(localService);
+			String myTraceFileLog = "/tmp/lsp4j-trace.log";
+			try {
+				final File myFile = new File(myTraceFileLog);
+				final PrintWriter printWriter = new PrintWriter(myFile);
+				this.messageTracer = new MessageTracer(printWriter);
+				System.out.println("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
+				System.out.println("LSP4J Trace logging to " + myTraceFileLog + ".");
+				System.out.println("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
+			} catch (FileNotFoundException e) {
+				System.out.println("Could not open " + myTraceFileLog +". Will not trace log.");
+			}
 			return this;
 		}