Closing parentheses were often highlighted as errors.
Add a syntax sync command to reduce the error.
Also fix that `defined` was not highlighted as an operator inside
parentheses. E.g.:
```
if defined foo (
if defined bar (
...
)
)
```
The first `defined` was highlighted but the second one was not.
related: #15453
Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
11c92be897
