busybox: update to latest version 1.21.1

Change makefile to use default .config file based on busybox version
bzip2: change mk-file to make it compile on x86_64
bzr: update bzr and used python

Use latest bzr version 2.6.0 and switch from using python 2.5 and python 2.6
to python 2.6 and python 2.7