Removed the default argument to the is_dlib_thread() function and

instead added an overload that doesn't take any arguments.  I did this
because -O3 sometimes makes gcc ignore more complex default arguments.
I don't actually have any cases where this happened to this function
but I'm changing it just to be safe.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402549

dlib/threads/threads_kernel_shared.cpp

@@ -306,6 +306,12 @@ namespace dlib
         return threads_kernel_shared::thread_pool().is_dlib_thread(id);
     }
 
+    bool is_dlib_thread (
+    )
+    {
+        return is_dlib_thread(get_thread_id());
+    }
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/threads/threads_kernel_shared.h

@@ -199,7 +199,10 @@ namespace dlib
     }
 
     bool is_dlib_thread (
-        thread_id_type id = get_thread_id()
+        thread_id_type id 
+    );
+
+    bool is_dlib_thread (
     );
 
 // ----------------------------------------------------------------------------------------