how do I remap backspace combinations? I can remap backspace itself in normal mode, but not in insert mode, and I cannot map combinations:

```
" this works:
nmap <BS> dd

" this doesn't work:
imap <BS> <Esc>dd
nmap <C-BS> dd
imap <C-BS> <Esc>dd

```

I'm using Vim 7.4 inside Terminator.