[git commit master] shell: consolidate builtin_foo.? into shell_common.?; delete obsolete shells

[Denys Vlasenko]

commit: http://git.busybox.net/busybox/commit/?id=599ae1eb9f20b4731735e14f9bac6371ad89b6d7
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>

Patch is too large, so refusing to show it