[js] compiler: remove direct call to compiler. Will be in a designated function
[js] compiler: rename init/uninit functions. hide other API for now
[js] compiler: stub implementation
[js] js_utils double inclusion protection
[js] compiler: input validation
[js] compiler: no need to compile built-in functions
[js] compiler: call compiler code. doesn't regard output
[js] compiler: function->code is now an opaque pointer with a destructor so it could be used to store compiled code as well as scan_t code