compiler: add support for shorthand method declarations

[jow-]

Add support for ES6-style shorthand method syntax in object literals. This allows declaring methods without the function keyword:

obj = {
    foo() { return 42; },
    add(a, b) { return a + b; },
    sum(...args) { ... }
};

[systemcrash]

Is this ready for prime-time?

[systemcrash]

I get

ucode/compiler.c:2136:10: warning: unused variable 'slot' [-Wunused-variable]
 2136 |         ssize_t slot;
      |                 ^~~~
1 warning generated.

other than that test complete OK.