[WebAssembly] Add pass to infer prototypes for prototype-less functions

See https://bugs.llvm.org/show_bug.cgi?id=35385

Differential Revision: https://reviews.llvm.org/D48471

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336759 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed