package/mtr: use ncurses option

Use --with-ncurses and --without-ncurses options which are available
since version 0.88 and
https://github.com/traviscross/mtr/commit/4e2a948a167d9b8a0a63b46a423d4ae1519ad759



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>