link-time optimization support

[Kim Barrett]

We've recently been getting a number of JBS issues filed that relate to
building with LTO (e.g. configure with 
--enable-jvm-feature-link-time-opt). It
looks to me as if LTO is not even close to actually working. Rather than 
deal
with this piecemeal at this seemingly random time, it seems to me that this
feature ought to be approached as a distinct project, with the first step
being a discussion about whether we even want to pursue it at this time.