fixup! Added rootfs overlay. Location is consistent with section 9.1 of buildroot manual.
Patch 1 of N: added menu option to enable D
Bumped GCC and binutils versions, because GDC 4.9 is (probably) significantly better than GDC 4.8
BUG FIX: GDC can't link against uClibc - changing to eglibc.
This increases the rootfs size from 22 MB to 30 MB.