functionality to handle global atoms in Merge sections

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@175636 91177308-0d34-0410-b5e6-96231b3b80d8
rename fixupAddend to relocAddend

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@175638 91177308-0d34-0410-b5e6-96231b3b80d8