MIPS update and tree re-sync with GPL 2678 from RT-N16:
Cleaned a few prebuild/prebuilt paths to be in-sync with GPL.
Fixed out-of-sync code with GPL for u2ec
Fixed out-of-sync makefiles with GPL for nvram
toolchain: Added the 4.2.3 toolchain Asus now uses to compile the MIPS kernel.
I suspect this is so Broadcom-provided modules such as ctf will be compiled with
the same toolchain as the rest of the kernel.
toolchain: remove the Kernel 2.4 toolchain - we don't have any model based on Kernel 2.4
toolchain: remove unused symlink
Updated documentation