[krbdev.mit.edu #8795] configure: chech for libncursesw, if libncurses is not found

[Greg Hudson via RT]

What platform does this problem apply to?

Ideally I'd like to use pkg-config here, but I don't think readline 
provides a pkg-config file.

Alternatively, we could eliminate the -lncurses (and possibly -lhistory 
since I think we don't use it directly) and just assume that the 
platform has functional library dependencies and a shared libreadline.