Bug#744095: Set default gcc-4.8 as default for mips64(el)

[Yunqiang Su <wzssyqa@gmail.com>]

Package: src:gcc-defaults
Version: 1.126

Hi, as I test, gcc-4.8 and gcc-4.9 work well on mips64el.
So please set gcc-4.8 as default in sid,
and set gcc-4.9 as default in experimental.

Please take care mips64/mips64el in future when bump the
default version in sid to 4.9.

Thank you.

-- 
Yunqiang Su