Add wakeful IO executor.

bramble-core/src/main/java/org/briarproject/bramble/system/DefaultWakefulIoExecutorModule.java

@@ -0,0 +1,23 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.system.WakefulIoExecutor;
+
+import java.util.concurrent.Executor;
+
+import dagger.Module;
+import dagger.Provides;
+
+/**
+ * Provides a default implementation of {@link WakefulIoExecutor} for systems
+ * without wake locks.
+ */
+@Module
+public class DefaultWakefulIoExecutorModule {
+
+	@Provides
+	@WakefulIoExecutor
+	Executor provideWakefulIoExecutor(@IoExecutor Executor ioExecutor) {
+		return ioExecutor;
+	}
+}