Fix Comment position with optional is used.

[AkihiroUeda35]

If a field is optional and has a leading comment, leading comment is written before "has_field".

message Sample {
  // Comment
  optional int32value = 1;
}

typedef struct _SampleMessage {
    /* Comment*/
    bool has_value;
    int32_t value;
} SampleMessage ;

In this condition, Intellisense comment of VS code is shown on has_value field.
With this change, comment position is on appropriate position as shown below.

typedef struct _SampleMessage {
    bool has_value;
    /* Comment*/
    int32_t value;
} SampleMessage ;

[PetteriAimonen]

I'm not sure which is better. When reading code directly, it makes more sense to have the comment before has_field.

[AkihiroUeda35]

Thank you for your comment.
Then, how do you think if generated code becomes as shown below?

typedef struct _SampleMessage {
    /* Comment*/
    int32_t value;
    bool has_value;
} SampleMessage ;

[PetteriAimonen]

That won't work, has_value has to precede the value for the descriptor offsets to remain in range.