ELF: Merge ELF{Object,DSO}Reader implementations.
ELF: Merge ELF{Object,DSO}Reader implementations.

The two classes are the same other than a few exceptions.
This patch merges them using templates.

git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@234060 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld