Adjust clang for change to APFloat::toString.

I changed the diagnostic printing code because it's probably better
to cut off a digit from DBL_MAX than to print something like
1.300000001 when the user wrote 1.3.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189625 91177308-0d34-0410-b5e6-96231b3b80d8