squishyball: port to ncurses-6.3
Without the change build on `ncurses-6.3` fails as:
mincurses.c: In function 'setup_term_customize':
mincurses.c:345:20: error: 'TERMINAL' {aka 'struct term'} has no member named 'Nttyb'
345 | term = cur_term->Nttyb;
| ^~
While at it update homepage from svn repository to gitlab one.