Fixed bug in hubbe_search() on wide strings.

The last character for 16-bit wide and last three characters
for 32-bit wide haystack strings was missed.

This bug was probably hard to trigger in practice, since
the hubbe_search() method is only used for needles longer
than 34 characters and satisfying some other more obscure
criteria, and to be triggered also requires a haystack of
a specific length compared to the needle.
Image._XPM: Fixed memory zapping bug in _xpm_write_rows().

The bug triggered in 3 bytes/pixel mode for colors where
the last byte of the colorcode was greater than 127, and
resulted in an semi-random 512 byte block of memory being
cleared for each such color entry.