[WebAssembly] Define WebAssembly-specific relocation codes.

Currently WebAssembly has two kinds of relocations; data addresses and
function addresses. This adds ELF relocations for them, as well as an
MC symbol kind to indicate which type of relocation is needed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257416 91177308-0d34-0410-b5e6-96231b3b80d8
21 files changed