[[ emscripten ]] Add WebAssembly build target and standalone builder options

This patch adds a new emscripen-wasm build target and renames the current emscripten target to emscripten-js. This allows the building of both WebAssembly and asm.js versions of the emscripten standalone engine. In addition the standalone builder and deploy scripts have been modified to handle building HTML5 standalones using either of these target architectures.

Note This PR depends on the following thirdparty & ide pull requests: https://github.com/livecode/livecode-thirdparty/pull/144 https://github.com/livecode/livecode-ide/pull/2129