This is a piece of a larger refactoring.  I'm postponing the larger 
refactoring until next stage1 -- I have some concerns about the 
compile-time impact that I'll need to measure.

In the mean time I want to get knowledge of the freelists out of 
pass_release_ssa_names::execute.  The larger refactoring will move the 
freelists into a class and pass_release_ssa_names won't have access to 
those private members.  So the guts of that routine have been moved into 
what will ultimately be a method of the name manager.

I'm also including a leak detector/verification routine for the 
freelists.  This version will bootstrap on the trunk if the verifier is 
enabled at the end of flush_ssanames_freelist.  However, the vectorizer 
leaks names horribly, thus it won't pass a regression test or a -O3 
bootstrap.  In the mean time, the verifier is still useful to help find 
leaks -- it's obviously not checking by default and the code is marked 
as a debug function.

This wraps up the things I expect to address during this stage1 cycle. 
I've got a fair amount of patch review to cover in the immediate future 
as well as starting the bugfixing cycle.

Bootstrapped and regression tested on x86_64-linux-gnu.  Installed on 
the trunk.

Jeff