perf ui: Introduce struct perf_error_ops

The struct perf_error_ops is for flexible error logging.

We can register appropriate functions based on front-end.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338265382-6872-4-git-send-email-namhyung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/debug.c b/tools/perf/util/debug.c
index efb1fce..4dfe0bb 100644
--- a/tools/perf/util/debug.c
+++ b/tools/perf/util/debug.c
@@ -47,7 +47,7 @@
 	return ret;
 }
 
-#ifdef NO_NEWT_SUPPORT
+#if defined(NO_NEWT_SUPPORT) && defined(NO_GTK2_SUPPORT)
 int ui__warning(const char *format, ...)
 {
 	va_list args;