[Patch] mt_allocator: spare mem & fix alignment problems

[Benjamin Kosnik]

>Well, I'm happy to report (after all basic_string is my (old) baby ;) 
>that with std::string it does *not* fail...

'tis as I feared.

>Is it possible that actually rope is not as thread-safe as was supposed 
>to be??

...rope certainly seems implicated. It is strange, however, that this
only fails with __mt_alloc and not with new_allocator or __pool_alloc.

We need to deprecate rope. We have no evidence that it's being used, and
it's the sole user of other crusty files. People who are curious about
it can just dig through the archives.

I'll propose a patch to do so immediately after 3.4.0.

-benjamin