Put preloaded files on HEAP instead of another ArrayBuffers.
Specialize Array/TypedArray in allocate() to avoid unnecessary array constructions.
1. mmap(): Make use of files that is backed by HEAP.
2. mmap(): Use valloc() directly.
3. mmap(): Try to avoid Array.slice() when possible.
Assert that MAP_SHARED is only specified with files backed by HEAP.
mmap(): Align to malloc's default alignment instead of pages.
Unleash the 4k alignment of mmap() in the test_mmap().
Make a temporary variable local.
Conform to coding conventions.