gcc: switch to gcc 4.8.x as the default compiler version

gcc 4.7.x is going to be retired soon, and now that gcc 4.9.0 is out,
it's time for Buildroot to switch to gcc 4.8.x as the default gcc
compiler version.

See https://gcc.gnu.org/ml/gcc/2014-05/msg00324.html for details about
gcc 4.7.x life cycle.

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

package/gcc/Config.in.host

@@ -11,7 +11,7 @@ choice
 	default BR2_GCC_VERSION_4_8_ARC if BR2_arc
 	default BR2_GCC_VERSION_4_9_X if BR2_microblaze || BR2_powerpc64le
 	default BR2_GCC_VERSION_4_5_X if BR2_bfin
-	default BR2_GCC_VERSION_4_7_X
+	default BR2_GCC_VERSION_4_8_X
 	help
 	  Select the version of gcc you wish to use.