I've read that page, and the javaApiLinks directive led me to the
default Java API links. This is from the current version (I've checked the source), so it appears that version 2.9.1 simply has no support for Java 8.
I have tried to specify the javaApiLinks like the default links (using only Java 7 and 8), but api_1.8 didn't work...
Perhaps the only way for now is to disable automatic linking and manually specify the link. The problem with that is that the Java 8 javadoc doesn't support (external) links yet - it can find the classes if you point to the package-list file but then the package-list file becomes part of the URL, or it can't find the package-list file. See
this post for more info.