added ccache, cflow, cgdb, NASM, Yasm

Signed-off-by: Fotis Georgatos <fotis.georgatos@uni.lu>
whitespace & header improvements

Signed-off-by: Fotis Georgatos <fotis.georgatos@uni.lu>
adjust cgdb to include libreadline as a dependency

Signed-off-by: Fotis Georgatos <fotis.georgatos@uni.lu>
Merge pull request #91 from fgeorgatos/contrib_assemblers_build_debug

add ccache, cflow, cgdb, NASM, Yasm