Factor out the addend encoding into a helper function and simplify the
processRelocationRef.
Also add a few simple rtdyld tests. More tests to come once GOTs can be tested too.
Related to <rdar://problem/17768539>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213689 91177308-0d34-0410-b5e6-96231b3b80d8