Fix segfault in 2006/birken under macOS

The problem was a missing +1 for strlen() in a malloc() call.

This entry still uses gets() and strangely changing it to fgets() makes
it segfault but I'll worry about this later when more entries have been
checked and (if possible) fixed.

2006/birken/birken.c

@@ -64,7 +64,7 @@ _=z->o; c=_->o->_; a= c->_->_->o; c=_
 ->c++; h(c); } Q Z(a->c<c->c){ a
 ->c++; h(a); } z=z->_; } } X*
 v(X*_,int O){ X*s=(X*)m\
-alloc(strlen(_)*siz\
+alloc(1+strlen(_)*siz\
 eof(X)); X*l=s;
 J((*l++=*_?
 *_-O:0)