[WebAssembly] Update dylink section parsing

This updates the format of the dylink section in accordance with
recent "spec" change:
  https://github.com/WebAssembly/tool-conventions/pull/77

Differential Revision: https://reviews.llvm.org/D55609

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@348989 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed