Add @SuppressWarnings("FallThrough") on generated lexer. (#454)

* Enabled Error-prone FallThrough WARN in Bazel

* Add @SuppressWarnings("FallThrough") on generated lexer.

* Let Travis use the project's bazelrc

Author: regisd

.bazelrc

@@ -0,0 +1,4 @@
+# https://errorprone.info/
+# TODO(#222) Increase to error when we build from jflex-1.7.1 with a lexer annotated with
+# @SuppressWarnings
+build --javacopt "-Xep:FallThrough:WARN"

.ci.bazelrc

@@ -1,3 +1,5 @@
+import %workspace%/.bazelrc
+
 # This is from Bazel's former travis setup, to avoid blowing up the RAM usage.
 startup --host_jvm_args=-Xms2000m
 startup --host_jvm_args=-Xmx3000m

jflex/src/main/java/jflex/Emitter.java

@@ -434,6 +434,9 @@ private void emitUserCode() {
   }
 
   private void emitClassName() {
+    // TODO(#222) Actually fix the fall-through violations
+    println("// See https://github.com/jflex-de/jflex/issues/222");
+    println("@SuppressWarnings(\"FallThrough\")");
     if (scanner.isPublic) print("public ");
 
     if (scanner.isAbstract) print("abstract ");