Use https and fix Guava reference version.

Author: Capstan

project.gradle

@@ -47,9 +47,9 @@ dependencies {
 /*
  * External javadoc links
  */
+// FIXME: For some reason, making this https causes OpenJDK 11 to fail.
 javadoc.options.links("http://docs.oracle.com/javase/6/docs/api/");
-javadoc.options.links("http://www.javadoc.io/doc/com.google.code.findbugs/jsr305/3.0.1/");
-javadoc.options.links("http://fasterxml.github.com/jackson-databind/javadoc/2.2.0/");
-javadoc.options.links("http://www.javadoc.io/doc/com.google.guava/guava/28.1-jre/");
-javadoc.options.links("http://fge.github.io/msg-simple/");
-
+javadoc.options.links("https://www.javadoc.io/doc/com.google.code.findbugs/jsr305/3.0.1/");
+javadoc.options.links("https://fasterxml.github.io/jackson-databind/javadoc/2.2.0/");
+javadoc.options.links("https://www.javadoc.io/doc/com.google.guava/guava/25.1-jre/");
+javadoc.options.links("https://fge.github.io/msg-simple/");