WebAssembly support

Implement support for a web-assembly backend in the compiler.

A bounty has been put in escrow in the foundation account, Karoly Balogh started an implementation, Dmitry Boyarintsev implemented a first working version: conway's game of life was shown to compile and run in the browser.

It was discovered that existing free tools do not provided the necessary relocatoin mechanisms for the LLVM linker, so an own assembly writer has been written by Dmitry.

Currently Nikolay Nikolov from the core team has taken over development of this feature.