DHCP options block from the contents.

encapsulated option; this will be needed for modifications to the options
block.

- value of n passed to wgetnstr should now be equivalent to output from strlen (i.e. length excluding NUL-terminating character)

- reimplemented cleaner wgetnstr
- fixed wdelch for use with _wcursback

- added mucurses_test.c build targets

multiple option sources (e.g. multiple DHCP replies, non-volatile
storage etc.)

getting key_ codes instead

- changes made to some constants and macros
- changes made to _curses_screen struct
- identified and removed prototypes for yet more unsupportable functions

- wgetch now includes non, part and full blocking read support

we are constructing the IP header ourselves.

Formatting fix-ups (80 column limit is mandatory!)

- some minor preventatives

- no longer depends on slk