Patch for Review: JvGetStringUTF and JvTempCString

[Tom Tromey]

Bryce> As for JvTempCString, do you have an example of when this is needed?
Bryce> What is wrong with, in client code, simply using JvGetStringUTF into a
Bryce> stack allocated buffer? I think it is better to keep CNI simple unless
Bryce> there is a compelling reason to have this.

I wanted it for use inside libgcj, to simplify existing code.

Also, in some cases it isn't clear that just using a stack allocated
buffer is best.  It seems a little better to me to put a size limit
on this.

Tom