[WebAssembly] Add hasSideEffects flag to catch instructions

Summary:
`catch` instruction certainly has rather huge side effects and the flag
was missing. At the moment this does not change any unit tests we
currently have.

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D50919

llvm-svn: 340433