[WebAssembly] Add WasmEHFuncInfo for unwind destination information

Summary:
Add WasmEHFuncInfo and routines to calculate and fill in this struct to
keep track of unwind destination information. This will be used in
other EH related passes.

Reviewers: dschuff

Subscribers: sbc100, jgravelle-google, sunfish, chrib, llvm-commits

Differential Revision: https://reviews.llvm.org/D48263

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335005 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed