gcc: add support for gcc 4.8

This commit adds support for the recently released gcc 4.8. We re-add
the same patch series as the one used for 4.7.x, after refreshing the
patches.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>