compiler/parser: invalid behaviour with struct composite literals

[zapateo]

Consider this code:

package main

type T struct { A, B int}

func main() {
	_ =  T{
		A: 10,
		B: 20
	}
}

The parser should return error:

syntax error: unexpected newline, expecting comma or }

but, instead, it accepts the code as it is correct.

Note that the same problem also involves the templates (add this test to test/misc/templates_test.go):

"BUG": {
	sources: fstest.Files{
		"index.html": `{%%
			_ = struct{A, B int} {
				A: 1,
				B: 2
			}
			%%}
		`,
	},
},