New toolchains Gcc 4.7.3 and Gcc 4.8.1 with Glibc 2.18

Adding toolchains with Gcc 4.7.3, Gcc 4.8.1 and Glibc 2.18.
Adding libqt4-embedded that will require the new toolchains.
These extensions have been tested on cedarview and 88f6281, but should also work for bromolow and x86.

Part 2 of 3: The new toolchain packages toolchain-gcc47 and toolchain-gcc48.