LUCENE-10239: upgrade jflex (1.7.0 -> 1.8.2) (#452)

Upgrade jflex.

Change doesn't alter the behavior of any of the analyzers (unicode
version or grammar refactorings), just the minimal to get new tooling
working.

buildSrc/scriptDepVersions.gradle

@@ -26,7 +26,7 @@ ext {
       "ecj": "3.25.0",
       "flexmark": "0.61.24",
       "javacc": "7.0.4",
-      "jflex": "1.7.0",
+      "jflex": "1.8.2",
       "jgit": "5.9.0.202009080501-r",
   ]
 }

dev-tools/missing-doclet/src/main/java/org/apache/lucene/missingdoclet/MissingDoclet.java

@@ -331,7 +331,7 @@ private boolean hasInheritedJavadocs(Element element) {
     if (hasOverrides) {
       // If an element has explicit @Overrides annotation, assume it does
       // have inherited javadocs somewhere.
-      reporter.print(Diagnostic.Kind.NOTE, element, "javadoc empty but @Override declared, skipping.");
+      // reporter.print(Diagnostic.Kind.NOTE, element, "javadoc empty but @Override declared, skipping.");
       return true;
     }
 
@@ -348,7 +348,7 @@ private boolean hasInheritedJavadocs(Element element) {
             // We could check supMethod for non-empty javadoc here. Don't know if this makes
             // sense though as all methods will be verified in the end so it'd fail on the
             // top of the hierarchy (if empty) anyway.
-            reporter.print(Diagnostic.Kind.NOTE, element, "javadoc empty but method overrides another, skipping.");
+            // reporter.print(Diagnostic.Kind.NOTE, element, "javadoc empty but method overrides another, skipping.");
             return true;
           }
         }

gradle/generation/jflex.gradle

@@ -270,6 +270,17 @@ class JFlexTask extends DefaultTask {
       ]
     }
 
+    // fix invalid SuppressWarnings from jflex, so that it works with javac.
+    // we also need to suppress 'unused' because of dead code, so it passes ecjLint
+    // you can't "stack" SuppressWarnings annotations, jflex adds its own, this is the only way
+    // https://github.com/jflex-de/jflex/issues/762
+    project.ant.replace(
+          file: target,
+          encoding: "UTF-8",
+          token: 'SuppressWarnings("FallThrough")',
+          value: 'SuppressWarnings({"fallthrough","unused"})'
+    )
+
     // Correct line endings for Windows.
     project.ant.fixcrlf(
         file: target,