html-xml-utils: fix and bump to 6.9

6.4 had a compile error:

```
scan.l:136:7: error: expected identifier or ‘(’ before ‘__extension__’
char *strndup(const char *s, size_t n);
^
```

This is caused by the standard library strndup() now living in string.h
and conflicting with another strndup() declared in scan.l.  Version 6.9
fixes this.

This also removes the need for the boolean patch that we previously had.