Move BinaryRef to a new include/llvm/Object/YAML.h file.

It will be used for ELF dumping too.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183287 91177308-0d34-0410-b5e6-96231b3b80d8
Handle (at least don't crash on) relocations with no symbols.

Should fix the MCJIT tests on PPC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183288 91177308-0d34-0410-b5e6-96231b3b80d8