When shrinking a mmap based allocation, we can just unmap the trailing
pages that will no longer be needed. When extending an allocation we try
to MMAP_FIXED_NOREPLACE the need extra data to avoid memcpy between old
and new allocation. I'm not sure if the extension logic is really worth
it but it is just 15 lines of code to avoid possibly very large memcpys.
Bananymous
b611c3fe48