Pick better floating point numbers (ones that can be exactly represented) in floating point instead of something that can't to avoid test suite failures on different devices and architectures.

<rdar://problem/18826900>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@221468 91177308-0d34-0410-b5e6-96231b3b80d8