Use the gcc sources from the official gcc arm-embedded branch instead of
the Haiku branch. These include patches adding support for complex
multilib setups for ARM, so the toolchain can now target armv6, and armv7
m/ar/em.
Enable said option so we get a multilib toolchain.
This also means we get gcc 4.8.4 instead of 4.8.2.
Bump revision of newlib since it was also rebuilt with multilib
support.
31bea66ae0