Update to buildroot toolchain for nios2

Thank for the reminding from marc. We shall keep it.

I would like to give my best thanks to marc and vapier.

I reminded vapier of the prior post from marc, bug# 273.

I did patch some of the *.S code to nios2 for the new abi in uClibc 0.9.28/29, bug# 616-618.

Most of the works came from marc, I just learn and follow him.

Vapier has been always helpful to sync up the patches. psm gives some helpful hints, too.

These are works in progress.

And still need a lot of tests and fixs, which all you can help.