gcc package refined

Hi there,
Here's the refined pull-request for an on-target gcc.

Changes since previous PR: 
* all commits properly signed-off-by
* uses gcc 4.8.3 instead of 4.6.3
* tested with BB toolchain, works

Tested by compiling and running C and C++ hello world samples from https://en.wikipedia.org/wiki/List_of_Hello_world_program_examples on target (ar71xx for now).