dbus-c++: Add functions with different return type to suppress clang warning

In dispatcher.h, if DBUS_HAS_RECURSIVE_MUTEX is not defined, we have function types

typedef bool (*MutexFreeFn)(Mutex *mx);
typedef bool (*MutexLockFn)(Mutex *mx);

But the implementation has the return type of void.

        static void mutex_free(Mutex *mx)
        {
                delete mx;
        }

        static void mutex_lock(Mutex *mx)
        {
                mx->lock();
        }

So it causes a function mismatch when calling _init_threading.

This patch adds new functions return bool if DBUS_HAS_RECURSIVE_MUTEX is not defined.
The new functions simply return false, it may not be correct, but it neither does
worse than current behavior which return random values.

TEST=USE="chrome_internal" CFLAGS="-clang -print-cmdline" CXXFLAGS="-clang -print-cmdline" emerge-x86-alex chaps
BUG=chromium-os:35315

Change-Id: I6e183f4fa403854357565544229c03b078c444c6
Reviewed-on: https://gerrit.chromium.org/gerrit/40897
Reviewed-by: Scott James Remnant <keybuk@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Denis Glotov <glotov@chromium.org>
Commit-Queue: Guozhi Wei <carrot@google.com>
Tested-by: Guozhi Wei <carrot@google.com>
diff --git a/include/dbus-c++/dispatcher.h b/include/dbus-c++/dispatcher.h
index 8e74b64..1b2b1d2 100644
--- a/include/dbus-c++/dispatcher.h
+++ b/include/dbus-c++/dispatcher.h
@@ -265,6 +265,19 @@
 		return new Mx;
 	}
 
+#ifndef DBUS_HAS_RECURSIVE_MUTEX
+	static bool mutex_free(Mutex *mx)
+	{
+		delete mx;
+		return false;
+	}
+
+	static bool mutex_lock(Mutex *mx)
+	{
+		mx->lock();
+		return false;
+	}
+#else
 	static void mutex_free(Mutex *mx)
 	{
 		delete mx;
@@ -274,6 +287,7 @@
 	{
 		mx->lock();
 	}
+#endif//DBUS_HAS_RECURSIVE_MUTEX
 
 	static void mutex_unlock(Mutex *mx)
 	{