Add build dependency on parboiled to fix build of documentation.

Updating JaCoCo in commit 23072ffb broke the build of the
HTML documentation. As found out by @chirontt, adding parboiled
as a build dependency fixes it.

Fixes #1220 and closes #1313

build.moxie

@@ -190,3 +190,4 @@ dependencies:
 # Dependencies with the "build" scope are retrieved
 # and injected into the Ant runtime classpath
 - build 'org.jacoco:org.jacoco.ant:0.7.8'
+- build 'org.parboiled:parboiled-java:1.1.7'