The UTF16 string referenced by a CFString should go into the __TEXT,__ustring

The UTF16 string referenced by a CFString should go into the __TEXT,__ustring
section. A 'normal' string will go into the __TEXT,__const section, but this
isn't good for UTF16 strings. The __ustring section allows for coalescing, among
other niceties (such as allowing the linker to easily split up strings).

Instead of outputting the UTF16 string as a series of bytes, output it as a
series of shorts. The back-end will then nicely place the UTF16 string into the
correct section, because it's a mensch.
<rdar://problem/10655949>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153710 91177308-0d34-0410-b5e6-96231b3b80d8