lang/smalltalk: use modern memory management

[brooks]

Summary

The memory allocator defaults to some horrifying complex code to manage
mmap'd allocations. On system where MAP_NORESERVE is defined (Linux) it
uses a much simpler approach relying on memory overcommit. Enable this
code on FreeBSD by defining MAP_NORESERVE to 0 (all allocations
are MAP_NORESERVE on FreeBSD unless a sysctl is set).

Entierly disable the other code path as it (somewhat gratutiously) uses
sbrk.

[brooks]

Bump PORTREVISION

[brooks]

I've built and tested this to the level of running hello world on an amd64 build without sbrk.

[danfe]

@brooks wrote:

The memory allocator defaults to some horrifying complex code to manage mmap'd allocations.

Thank you for doing this Brooks, much appreciated! I've tried this myself back in summer but was demotivated by this horrible complexity and didn't complete the quest.

I've built and tested this to the level of running hello world on an amd64 build without sbrk(2).

Good enough for me, please go ahead and commit.