Fix: buffer overflow when entering long epitaph

[entrez]

Providing a char[101] buffer to getlin didn't actually limit user input to 100 characters; instead it ensured anything longer would end up written past the end of the buffer. Not possible in TTY (since for some reason getlin input length is limited to COLNO, getline.c:146) but in curses this could be done and cause a crash on some platforms, or potentially be put to some other malicious end. Prevent this from happening (and remove the 100 character limit, since it's not actually enforced when entering text; instead, limit the full epitaph to the size of the buffer).

I also changed things around so that selecting to enter your own epitaph, but then entering an empty line, will use the default formatkiller headstone engraving.