[PATCH] Remove volatile qualifiers from mt_allocator

[Paolo Carlini]

Paolo Carlini wrote:

> Note that we are going to change class layout anyway (and probably we 
> can live with that because that isn't the default allocator, etc...), 
> because currently _M_used is an array of size_t and would become an 
> array of int. Actually, on 64-bit machines I bet the "total" layout 
> would change less with a *pair* of ints as you are suggesting for 
> completely different reasons.

Sorry, I was wrong here: class layout would not change with the single 
_M_used atomics, because the class hosts a *pointer*, not the actual 
data. Ok... ;)

Paolo.