Add Checstyle FallThrough

Author: garydgregory

src/conf/checkstyle/checkstyle.xml

@@ -50,6 +50,7 @@ limitations under the License.
     </module>
     <module name="EqualsHashCode" />
     <module name="ExplicitInitialization" />
+    <module name="FallThrough" />
     <module name="FinalLocalVariable" />
     <module name="FinalParameters" />
     <module name="IllegalImport" />

src/main/java/org/apache/commons/csv/CSVPrinter.java

@@ -236,7 +236,7 @@ public synchronized void printComment(final String comment) throws IOException {
                 if (i + 1 < comment.length() && comment.charAt(i + 1) == LF) {
                     i++;
                 }
-                //$FALL-THROUGH$ break intentionally excluded.
+                // falls-through: break intentionally excluded.
             case LF:
                 println();
                 appendable.append(format.getCommentMarker().charValue()); // N.B. Explicit (un)boxing is intentional