- char16_t is a distinct type, so stay consistent
with it throughout the code base.
- char16_t is defined as minimum size of 16 bits.
Since we mmap and cast data structures onto raw memory,
we need a precise definition (uint16_t), so we cast between
that (and static_assert that they are the same size).
Change-Id: I869c32637543bbcfb39d2643e7d9df10d33acd3c
