cc/gcc: Add 4.7.4 and 4.8.3

Signed-off-by: Anton Leontiev <aleontiev@elvees.com>
kernel/linux: update kernel versions

Add 3.15.0, and update all other branch versions.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
kernel/linux: further bump the versions

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>