Add const version of OwningBinary::getBinary

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220231 91177308-0d34-0410-b5e6-96231b3b80d8
Constify getELFDynamicSymbolIterators standalone function. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220232 91177308-0d34-0410-b5e6-96231b3b80d8