Real solution for findLibraryInternal()

[Christian Ehrlicher]

Hi,

since nobody cares here's the reason why loading plugins on windows
doesn't work anymore. r990265 adds the lib prefix no matter if we're on
windows or not. I don't know why cygwin should be supported at all but
this checkin definitifly breaks any plugin on windows...

I've reverted it to make plugins work again. This should also fix bug
204874 which was fixed wrong but nobody cared either until someone did a
clean install on linux...

Christian