relax check for apidoc

nbbuild/javadoctools/template.xml

@@ -287,7 +287,8 @@ cause it to fail.
     </condition>
 
     <target name="javadoc-exec-packages" depends="javadoc-init,javadoc-generate-references,javadoc-generate-overview,javadoc-exec-condition,javadoc-check-timestamps,javadoc-make-plain-title,javadoc-make-hyperlinked-title,javadoc-exec-condition,-javadoc-set-footer" unless="javadoc.exec.packages">
-        <javadoc source="${javac.source}" failonerror="${apidoc.check}" failonwarning="${apidoc.check}" author="false" destdir="${javadoc.out.dir}" packagenames="${javadoc.packages}" stylesheetfile="${javadoc.css.main}" windowtitle="${javadoc.title}" overview="${javadoc.overview}" splitindex="true" use="true" version="false" useexternalfile="true" encoding="UTF-8">
+        <!-- -->
+        <javadoc source="${javac.source}" failonerror="${apidoc.check}" failonwarning="false" author="false" destdir="${javadoc.out.dir}" packagenames="${javadoc.packages}" stylesheetfile="${javadoc.css.main}" windowtitle="${javadoc.title}" overview="${javadoc.overview}" splitindex="true" use="true" version="false" useexternalfile="true" encoding="UTF-8">
             <sourcepath>
                 <pathelement location="${javadoc.docfiles}"/>
                 <pathelement location="${javadoc.src}"/>
@@ -314,6 +315,7 @@ cause it to fail.
             <bottom>${javadoc.footer}</bottom>
             <!-- Avoid timestamp comments in _all_ html generated files, to reduce unnecessary git commits -->
             <arg value="-notimestamp" />
+            <arg value="-Xdoclint:html,reference,syntax" />
         </javadoc>
     </target>
 
@@ -336,6 +338,7 @@ cause it to fail.
             <doctitle>${javadoc.title}&lt;br/&gt;${javadoc.stability.label}</doctitle>
             <header>${javadoc.header}</header>
             <bottom>${javadoc.footer}</bottom>
+            <arg value="-Xdoclint:html,reference,syntax" />
         </javadoc>
     </target>