Add BR2_DEPRECATED_SINCE_2014_08

In preparation for the deprecation of certain features in 2014.08, add
the BR2_DEPRECATED_SINCE_2014_08 symbol.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Config.in

@@ -319,6 +319,10 @@ config BR2_DEPRECATED_SINCE_2014_05
 	bool
 	default y
 
+config BR2_DEPRECATED_SINCE_2014_08
+	bool
+	default y
+
 endif
 
 config BR2_ENABLE_DEBUG