[ORC] Switch from shared_ptr to unique_ptr for addModule methods.

Layer implementations typically mutate module state, and this is better
reflected by having layers own the Module they are operating on.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327566 91177308-0d34-0410-b5e6-96231b3b80d8
17 files changed