Moscow ML crashes after allocating a lot of memory

[kfl]

Due to a change in GNU malloc, Moscow ML may crash on 64 bit architectures as well as on those 32 bit architectures that use glibc 2.7.

Originally reported by HOL developers

[kfl]

Can be fixed by disabling the use of mmap from malloc.

For example by adding
mallopt(M_MMAP_MAX, 0);
to `init_gc` in `gc_ctrl.c` before setting the minor heap size.

[kfl]

The above fix with mallopt is of cause just hiding the root cause.

It's more likely that the bug is to be found somewhere in the GC. For example, at
http://github.com/kfl/mosml/blob/Rel-2.10/src/runtime/memory.c#L45
we assign a negative value to an unsigned value. And at
http://github.com/kfl/mosml/blob/Rel-2.10/src/runtime/memory.c#L58
we free memory allocated by alligned_alloc.

[kfl]

This issue should now be fixed