perf ui browser: Honour the xterm colors

So slang after all _has_ a 'default' color, call me color blind. Change
the default to it.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Link: http://lkml.kernel.org/n/tip-1dfxivxv0jhwldpds3v4zla2@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/ui/browser.c

@@ -439,19 +439,19 @@ static struct ui_browser__colorset {
 		.colorset = HE_COLORSET_TOP,
 		.name	  = "top",
 		.fg	  = "red",
-		.bg	  = "black",
+		.bg	  = "default",
 	},
 	{
 		.colorset = HE_COLORSET_MEDIUM,
 		.name	  = "medium",
 		.fg	  = "green",
-		.bg	  = "black",
+		.bg	  = "default",
 	},
 	{
 		.colorset = HE_COLORSET_NORMAL,
 		.name	  = "normal",
-		.fg	  = "brightgreen",
-		.bg	  = "black",
+		.fg	  = "default",
+		.bg	  = "default",
 	},
 	{
 		.colorset = HE_COLORSET_SELECTED,
@@ -463,7 +463,7 @@ static struct ui_browser__colorset {
 		.colorset = HE_COLORSET_CODE,
 		.name	  = "code",
 		.fg	  = "blue",
-		.bg	  = "black",
+		.bg	  = "default",
 	},
 	{
 		.name = NULL,