[PATCH] add __ASSUME_MREMAP

[Roland McGrath]

> I see, malloc-sysdep.h seems a better fit then, assuming it is fine 
> using it outside of malloc itself.

It's not ideal but I don't have a real problem with it.

> Yes, that is what my patch does. Attached there is a new version of it, 
> updated after your feedback.

Send a patch that only touches malloc.  The libio issue is separate and can
be addressed afterwards.