Replace a mess of snprintf() dances with easier to read code using

Replace a mess of snprintf() dances with easier to read code using
strlcat(). Shorter, clearer, fewer signed vs unsigned questions.

Shrink static buffer for the string version of an option value from
32K to 8K. Since the string version of the entire lease is constructed
in a 8K buffer, bigger option values are pointless.

Use 8K of the saved space for a static buffer for pretty_print_string()
and use it rather scribbling intermediate values into the final
destination.

No intentional functional change.