Create CMake install targets for libs and JS files (#798)
Create CMake install targets for libs and JS files (#798)

This creates install rules for the binaryen shlib and the C header, as
well as for the various JS files (wasm.js and binaryen.js, as well as
those used by emscripten). It recreates in the install target the
current layout used by an in-tree build.
yurydelendik/binaryen,WebAssembly/binaryen,WebAssembly/binaryen,WebAssembly/binaryen,yurydelendik/binaryen,yurydelendik/binaryen,WebAssembly/binaryen,WebAssembly/binaryen,yurydelendik/binaryen,yurydelendik/binaryen