bug#16544: Optimazation for is_mb_middle

[Norihiro Tanaka]

Hi Paul,

Thank you for reviewing tha patch.

> Please use something like this instead

All right.

> A minor question about naming: in what sense is mbclen_guess a guess?  

Because mbclen_guess always returns -2 for characters of two or more bytes,
I consider that what isn't mbclen_cache should be used instead of it. But
I don't particularly attach one's mind to the name. Now, I rename it to
mbclen_cache.

is_mb_middle.txt
Description: Binary data