Fix PlatformDependent.newAtomic*FieldUpdater type safety

Motivation:

* newAtomicIntegerFieldUpdater and newAtomicLongFieldUpdater take a
class<?> so they're too lax
* newAtomicReferenceFieldUpdater takes a Class<U> so it's too strict
and can only be passe a rawtype parameter when dealing w/ generic
classes

Modifications:

Take a Class<? super T> parameter instead.

Result:

Better type safety and generics support.

common/src/main/java/io/netty/util/internal/PlatformDependent.java

@@ -416,7 +416,7 @@ public final class PlatformDependent {
      * use {@link AtomicReferenceFieldUpdater#newUpdater(Class, Class, String)} as fallback.
      */
     public static <U, W> AtomicReferenceFieldUpdater<U, W> newAtomicReferenceFieldUpdater(
-            Class<U> tclass, String fieldName) {
+            Class<? super U> tclass, String fieldName) {
         if (hasUnsafe()) {
             try {
                 return PlatformDependent0.newAtomicReferenceFieldUpdater(tclass, fieldName);
@@ -433,7 +433,7 @@ public final class PlatformDependent {
      * use {@link AtomicIntegerFieldUpdater#newUpdater(Class, String)} as fallback.
      */
     public static <T> AtomicIntegerFieldUpdater<T> newAtomicIntegerFieldUpdater(
-            Class<?> tclass, String fieldName) {
+            Class<? super T> tclass, String fieldName) {
         if (hasUnsafe()) {
             try {
                 return PlatformDependent0.newAtomicIntegerFieldUpdater(tclass, fieldName);
@@ -450,7 +450,7 @@ public final class PlatformDependent {
      * use {@link AtomicLongFieldUpdater#newUpdater(Class, String)} as fallback.
      */
     public static <T> AtomicLongFieldUpdater<T> newAtomicLongFieldUpdater(
-            Class<?> tclass, String fieldName) {
+            Class<? super T> tclass, String fieldName) {
         if (hasUnsafe()) {
             try {
                 return PlatformDependent0.newAtomicLongFieldUpdater(tclass, fieldName);

common/src/main/java/io/netty/util/internal/PlatformDependent0.java

@@ -269,17 +269,17 @@ final class PlatformDependent0 {
     }
 
     static <U, W> AtomicReferenceFieldUpdater<U, W> newAtomicReferenceFieldUpdater(
-            Class<U> tclass, String fieldName) throws Exception {
+            Class<? super U> tclass, String fieldName) throws Exception {
         return new UnsafeAtomicReferenceFieldUpdater<U, W>(UNSAFE, tclass, fieldName);
     }
 
     static <T> AtomicIntegerFieldUpdater<T> newAtomicIntegerFieldUpdater(
-            Class<?> tclass, String fieldName) throws Exception {
+            Class<? super T> tclass, String fieldName) throws Exception {
         return new UnsafeAtomicIntegerFieldUpdater<T>(UNSAFE, tclass, fieldName);
     }
 
     static <T> AtomicLongFieldUpdater<T> newAtomicLongFieldUpdater(
-            Class<?> tclass, String fieldName) throws Exception {
+            Class<? super T> tclass, String fieldName) throws Exception {
         return new UnsafeAtomicLongFieldUpdater<T>(UNSAFE, tclass, fieldName);
     }
 

common/src/main/java/io/netty/util/internal/UnsafeAtomicIntegerFieldUpdater.java

@@ -25,7 +25,8 @@ final class UnsafeAtomicIntegerFieldUpdater<T> extends AtomicIntegerFieldUpdater
     private final long offset;
     private final Unsafe unsafe;
 
-    UnsafeAtomicIntegerFieldUpdater(Unsafe unsafe, Class<?> tClass, String fieldName) throws NoSuchFieldException {
+    UnsafeAtomicIntegerFieldUpdater(Unsafe unsafe, Class<? super T> tClass, String fieldName)
+            throws NoSuchFieldException {
         Field field = tClass.getDeclaredField(fieldName);
         if (!Modifier.isVolatile(field.getModifiers())) {
             throw new IllegalArgumentException("Must be volatile");

common/src/main/java/io/netty/util/internal/UnsafeAtomicLongFieldUpdater.java

@@ -25,7 +25,8 @@ final class UnsafeAtomicLongFieldUpdater<T> extends AtomicLongFieldUpdater<T> {
     private final long offset;
     private final Unsafe unsafe;
 
-    UnsafeAtomicLongFieldUpdater(Unsafe unsafe, Class<?> tClass, String fieldName) throws NoSuchFieldException {
+    UnsafeAtomicLongFieldUpdater(Unsafe unsafe, Class<? super T> tClass, String fieldName)
+            throws NoSuchFieldException {
         Field field = tClass.getDeclaredField(fieldName);
         if (!Modifier.isVolatile(field.getModifiers())) {
             throw new IllegalArgumentException("Must be volatile");

common/src/main/java/io/netty/util/internal/UnsafeAtomicReferenceFieldUpdater.java

@@ -25,7 +25,8 @@ final class UnsafeAtomicReferenceFieldUpdater<U, M> extends AtomicReferenceField
     private final long offset;
     private final Unsafe unsafe;
 
-    UnsafeAtomicReferenceFieldUpdater(Unsafe unsafe, Class<U> tClass, String fieldName) throws NoSuchFieldException {
+    UnsafeAtomicReferenceFieldUpdater(Unsafe unsafe, Class<? super U> tClass, String fieldName)
+            throws NoSuchFieldException {
         Field field = tClass.getDeclaredField(fieldName);
         if (!Modifier.isVolatile(field.getModifiers())) {
             throw new IllegalArgumentException("Must be volatile");