toolchain-external: add Sourcery ARM 2013.11, remove Sourcery ARM 2011.09

This commit adds the support for the recently release Sourcery ARM
2013.11 toolchain (gcc 4.8, gdb 7.6, glibc 2.18), and consequently
removes the support for the Sourcery ARM 2011.09 toolchain.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>