Cheerp 2.0rc1 released - support for WebAssembly and mixed JavaScript-WebAssembly mode

Written for Cheerp by Stefano De Rossi on 2017-11-13

Cheerp 2.0 - release candidate 1 released today, adding support to WebAssembly and a new mixed JavaScript-WebAssembly compilation.

Changelog:

    * Add a WebAssembly backend that produces binary and textual wasm
    * Add flag -cheerp-asmjs-mem-file to output a file holding asm.js module initialized memory
    * Add flag -cheerp-wasm-loader to output a file that initialises the WebAssembly file
    * Add flag -cheerp-linear-heap-size that sets heap size in megabytes for asmjs and wasm
    * Add flag -cheerp-no-math-fround that disables the usage of Math.fround()

    * Add `[[cheerp::asmjs]]` attribute for setting globals in the asmjs section manually
    * Add `[[cheerp::genericjs]]` attribute for setting globals in the generic section
    * Enabling asmjs mode will define `__ASMJS__` in the preprocessor
    * Enabling wasm mode will define `__WASM__` in the preprocessor
    * Overhaul of priority system to remove useless parenthesis and type coercions