sed dumps core in new multibyte code

[Garrett D'Amore]

This tracks illumos 5158 : http://www.illumos.org/issues/5158

Example script that breaks :

echo x | sed 'y%,%,%'

Root problem is that 4th argument (ps) to mbsrtowcs() is null. This is specifically permitted. We need to assign this to an mbstate variable (static) at this time.

[Garrett D'Amore]

fixes #78 sed dumps core in new multibyte code 5158 sed dumps core in new multibyte code

→ <<cset c839cf6c28e9>>