Add BR2_GLIBC_VERSION_2_23=y in barreleye_defconfig

This makes it match other platforms, also requested in:
https://github.com/open-power/op-build/pull/366#issuecomment-194169050

Suggested-by: Johnny <jonnyhihi@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/barreleye_defconfig b/openpower/configs/barreleye_defconfig
index b6da7f9..930090b 100755
--- a/openpower/configs/barreleye_defconfig
+++ b/openpower/configs/barreleye_defconfig
@@ -6,6 +6,7 @@
 BR2_EXTRA_GCC_CONFIG_OPTIONS="--enable-targets=powerpc64-linux"
 BR2_TOOLCHAIN_BUILDROOT_CXX=y
 # BR2_TOOLCHAIN_BUILDROOT_LIBSTDCPP is not set
+BR2_GLIBC_VERSION_2_23=y
 
 BR2_OPENPOWER_CONFIG_NAME="barreleye"
 BR2_OPENPOWER_XML_PACKAGE="barreleye-xml"