Problem: SOUNDEX returned an invalid string for international
characters in multi-byte character sets.
For example: for a Chinese/Japanese 3-byte long character
_utf8 0xE99885 it took only the very first byte 0xE9,
put it into the outout string and then appended with three 
DIGIT ZERO characters, so the result was 0xE9303030 - which
is an invalide utf8 string.
Fix: make SOUNDEX() multi-byte aware and - put only complete
characters into result, thus return only valid strings.
This patch also makes SOUNDEX() compatible with UCS2.