[WebAssembly] Improve readobj and nm support for wasm

Now that the libObect support for wasm is better we can
have readobj and nm produce more useful output too.

Differential Revision: https://reviews.llvm.org/D31514

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300365 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed