New-line support for message constant field separator

[ii64]

Currently the parser does not support new-line separation for message constant field due to that only check for:

self.tokenizer.next_symbol_if_in(&[',', ';'])?;

Additionally, extra separator without field definition will also give an error.

Test data:

option (blabla) = {
  foo: bar
  baz: bur
  boo: biz
};

option (blabla) = {
  foo: bar,
  baz: bur,
  boo: biz,
};

rust-protobuf/protobuf-parse/src/pure/parser.rs

Lines 381 to 390 in a542121

	// Consume the comma or semicolon if present. Commas and semicolons
	// between message fields are optional, all these are valid:
	//
	// {foo: 1,bar: 2,baz: 3,}
	// {foo: 1;bar: 2;baz: 3;}
	// {foo: 1 bar: 2 baz: 3}
	// {foo: 1,bar: 2;baz: 3}
	// {foo: 1,bar: 2 baz: 3}
	//
	self.tokenizer.next_symbol_if_in(&[',', ';'])?;

Error:

Caused by:
    0: error in `<stripped>.proto`: at <stripped>:3: While parsing message constant, expecting char `}`
    1: at <stripped>:3: While parsing message constant, expecting char `}`
    2: While parsing message constant, expecting char `}`