<rdar://problem/12783351>

Add support for half-floats, as specified by IEEE-754-2008
With this checkin, you can now say:
(lldb) x/7hf foo

to read 7 half-floats at address foo



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@183716 91177308-0d34-0410-b5e6-96231b3b80d8