[LLVM-C] Add accessors to the default floating-point metadata node
Summary: Add a getter and setter pair for floating-point accuracy metadata.
Reviewers: whitequark, deadalnix
Reviewed By: whitequark
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60527
llvm-svn: 358883