Ruby

Use mmap for heap page allocation only

Currently, rb_aligned_malloc uses mmap if Ruby heap pages can be
allocated through mmap (when system heap page size <= Ruby heap page
size). If Ruby heap page sizes is increased to 64KiB, then mmap will
be used on systems with 64KiB system page sizes. However, the transient
heap also uses rb_aligned_malloc and requires 32KiB alignment. This
would break in the current implementation since it would allocate sizes
through mmap that is not a multiple of the system page size.

This commit adds heap_page_body_allocate which will use mmap when
possible and changes rb_aligned_malloc to not use mmap (and only
use posix_memalign).