Add several missing double constant definitions

These were present in CL 1.0, just not implemented yet.

v2: Use hex values and fix commit message

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Jeroen Ketema <j.ketema@imperial.ac.uk>
CC: Matt Arsenault <Matthew.Arsenault@amd.com>
llvm-svn: 213321