OpenCL C: Add support for a set of floating point 
arithmetic relaxation flags:

-cl-no-signed-zeros
-cl-unsafe-math-optimizations
-cl-finite-math-only
-cl-fast-relaxed-math

Propagate the info to FP instruction flags as well
as function attributes where they are available.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@223928 91177308-0d34-0410-b5e6-96231b3b80d8