Re: Upgrade build requirement to Java 13?

[Martin Desruisseaux]

Actually there is apparently a conflict between Java 11 and Java 13 
about the HTML header tags (<h2>, <h4>) that we are supposed to use in 
Javadoc comments. When the checks for HTML tags is enabled (which SIS 
build does), javac emit an error if unexpected numbers is used. Since we 
can not be compatible with both Java 11 and Java 13 (unless we disable 
the checks), I took the initiative to upgrade the build requirement to 
Java 13. Reminder: this is only for building SIS; the compilation result 
is still executable on Java 8.

If there is any objection against this move, I can try to restore the 
possibility to build with Java 11 using Maven profile.

    Martin