MB-8667 Make alloc_util allocators use malloc.

And also instruct malloc not to use mmaps.

In my testing it decreases the number of page faults during indexing
in about 20 times without noticeable difference in indexing time.

Even better results can be achieved by making erlang use malloc
without its own allocators on top. But this breaks
erlang:memory() and this quite useful memory information is also
missing from crash dumps. So for now we'll stick to current approach.

Change-Id: Iee4b98902d9855e6f95de1917bfeee9023bd18d9
Reviewed-on: http://review.couchbase.org/28929
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>