This implements basic support for compiling (though not yet assembling
or linking) for a WebAssembly target. Note that ABI details are not yet
finalized, and may change.
Differential Revision: http://reviews.llvm.org/D12002
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@246814 91177308-0d34-0410-b5e6-96231b3b80d8
Dan Gohman