Fix a couple of compiler bugs. topenv was getting initialized in multiple places. This resulted in multiple copies of modules getting created which caused problems for macro expansion. Additionally, arguments were not being marked as declared during code generation so assigning to an argument that was not closed over generated invalid C code.

#{
	main <- {
		arr <- json decode: "[\"foo\",  \"bar\", 13245, \"baz\"   ]"
		foreach: arr :idx val {
			print: (string: idx) . ": " . (string: val) . "\n"
		}
		obj <- json decode: "{\"foo\":    \"bar\",  \"baz\": \"qux\", \"meaningOfLife\": 42   }"
		foreach: obj :idx val {
			print: (string: idx) . ": " . (string: val) . "\n"
		}
	}
}