Use libbsddialog autosize for inputbox (at least for height for now). So delete f_dialog_inputbox_size() of bsdconfig because is built on dialog/Xdialog and could create some problem in the long term.
Moreover (not in screenshots), add a --hline string: "Use TAB and Enter to select OK", because the UI dialog/bsddialog is different: dialog does not require TAB to switch the focus on buttons for the inputbox. I could change this in the next version (form refactoring is in the TODO list).
```
┌────────────────────┤Set Hostname├────────────────────┐
│ Please choose a hostname for this machine. │
│ │
│ If you are running on a managed network, please ask │
│ your network administrator for an appropriate name. │
│┌────────────────────────────────────────────────────┐│
││fbsd.local ││
│└────────────────────────────────────────────────────┘│
├──────────────────────────────────────────────────────┤
│ [ OK ] │
└─────────── Use TAB and Enter to select OK ───────────┘
```