[m-rev.] for review: Use mmap for Boehm GC in threaded grades on Linux.

[Peter Wang]

On Fri, 25 Jul 2014 12:09:21 +1000, Peter Wang <novalazy at gmail.com> wrote:
> Branches: master
> 
> The glibc implementation of malloc (commonly used on Linux) can use sbrk
> to acquire more memory, and so does Boehm GC in its default configuration
> on Linux.  When both allocators are invoked simultaneously from different
> threads then memory corruption may result.

Committed to 14.01 branch as well.

Peter