Illegal reflective access by com.sun.mail.util.SocketFetcher

Connecting to a store while running on OpenJDK 11 produces the following warning.

WARNING: An illegal reflective access operation has occurred`
WARNING: Illegal reflective access by com.sun.mail.util.SocketFetcher (file:/home/olivier/.m2/repository/com/sun/mail/mailapi/1.6.3/mailapi-1.6.3.jar) to method sun.security.util.HostnameChecker.getInstance(byte)
WARNING: Please consider reporting this to the maintainers of com.sun.mail.util.SocketFetcher
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

The problem seems to lie in [`SocketFetcher#matchCert`](https://github.com/eclipse-ee4j/javamail/blob/master/mail/src/main/java/com/sun/mail/util/SocketFetcher.java#L683).

I can provide a detailed test case to reproduce the problem, but I suppose it is not necessary, as the source of the problem seems clear.