Update javadoc classpath to include Minecraft dependencies

Author: stephan-gh

src/main/java/net/minecraftforge/gradle/user/UserBasePlugin.java

@@ -36,6 +36,7 @@
 import org.gradle.api.artifacts.result.ResolvedArtifactResult;
 import org.gradle.api.file.ConfigurableFileCollection;
 import org.gradle.api.internal.plugins.DslObject;
+import org.gradle.api.plugins.JavaPlugin;
 import org.gradle.api.plugins.JavaPluginConvention;
 import org.gradle.api.plugins.MavenPluginConvention;
 import org.gradle.api.tasks.GroovySourceSet;
@@ -45,6 +46,7 @@
 import org.gradle.api.tasks.bundling.Jar;
 import org.gradle.api.tasks.compile.GroovyCompile;
 import org.gradle.api.tasks.compile.JavaCompile;
+import org.gradle.api.tasks.javadoc.Javadoc;
 import org.gradle.api.tasks.scala.ScalaCompile;
 import org.gradle.jvm.JvmLibrary;
 import org.gradle.language.base.artifact.SourcesArtifact;
@@ -475,6 +477,9 @@ protected void configureCompilation()
         project.getConfigurations().getByName("apiCompile").extendsFrom(project.getConfigurations().getByName("compile"));
         project.getConfigurations().getByName("testCompile").extendsFrom(project.getConfigurations().getByName("apiCompile"));
 
+        Javadoc javadoc = (Javadoc) project.getTasks().getByName(JavaPlugin.JAVADOC_TASK_NAME);
+        javadoc.setClasspath(main.getOutput().plus(main.getCompileClasspath()));
+
         // set the compile target
         javaConv.setSourceCompatibility("1.6");
         javaConv.setTargetCompatibility("1.6");