zsh bug: isearch doesn't support unicode properly

[Yichao Yu <yyc1992@xxxxxxxxx>]

Hi,

I've got a problem when typing unicode characters in the zsh's history search.

When trying to use unicode characters in isearch (the default binding
for ^S and ^R), some of the unicode characters are not recognized
correctly. For example, (with utf-8 encoding), when typing "重新安装"
(utf-8 string: \xe9\x87\x8d\xe6\x96\xb0\xe5\xae\x89\xe8\xa3\x85)
what's recognized by zsh is actually "駭涰宩裥" (utf-8 string:
\xe9\xa7\xad\xe6\xb6\xb0\xe5\xae\xa9\xe8\xa3\xa5e). It seems that the
fifth bit in one byte is flipped in come cases.

I'm not yet sure what's wrong with these characters but at least the
meta character processing looks suspicious.

Yichao Yu