Fix cases like
```
/*short comment*/ /*long
comment */
int mbedtls_foo;
```
where the previous code thought that the second line started outside of a
comment and ended inside of a comment.
I believe that the new code strips comments correctly. It also strips string
literals, just in case.
Fixes#5191.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
c8794202e6