Do not leak package-private class in public API

Reduces the 'protected' copy method to 'package-private'.

This issue was detected using the revapi maven plugin.
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL128.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL128.java
index 9617f1d..47ca144 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL128.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL128.java
@@ -181,5 +181,5 @@
      *
      * @return the copy
      */
-    protected abstract AbstractL128 copy();
+    abstract AbstractL128 copy();
 }
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL64.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL64.java
index 4509a6d..dabaf64 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL64.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/AbstractL64.java
@@ -146,5 +146,5 @@
      *
      * @return the copy
      */
-    protected abstract AbstractL64 copy();
+    abstract AbstractL64 copy();
 }
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X1024Mix.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X1024Mix.java
index 4728114..0417026 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X1024Mix.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X1024Mix.java
@@ -180,7 +180,7 @@
 
     /** {@inheritDoc} */
     @Override
-    protected AbstractL128 copy() {
+    AbstractL128 copy() {
         // This exists to ensure the jump function performed in the super class returns
         // the correct class type. It should not be public.
         return new L128X1024Mix(this);
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X128Mix.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X128Mix.java
index e5a0c35..8d905f2 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X128Mix.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X128Mix.java
@@ -197,7 +197,7 @@
 
     /** {@inheritDoc} */
     @Override
-    protected AbstractL128 copy() {
+    AbstractL128 copy() {
         // This exists to ensure the jump function performed in the super class returns
         // the correct class type. It should not be public.
         return new L128X128Mix(this);
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X256Mix.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X256Mix.java
index 26e78d7..16a1b0a 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X256Mix.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L128X256Mix.java
@@ -225,7 +225,7 @@
 
     /** {@inheritDoc} */
     @Override
-    protected AbstractL128 copy() {
+    AbstractL128 copy() {
         // This exists to ensure the jump function performed in the super class returns
         // the correct class type. It should not be public.
         return new L128X256Mix(this);
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X1024Mix.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X1024Mix.java
index 6fa62b8..d78b0f8 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X1024Mix.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X1024Mix.java
@@ -171,7 +171,7 @@
 
     /** {@inheritDoc} */
     @Override
-    protected AbstractL64 copy() {
+    AbstractL64 copy() {
         // This exists to ensure the jump function performed in the super class returns
         // the correct class type. It should not be public.
         return new L64X1024Mix(this);
diff --git a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X256Mix.java b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X256Mix.java
index eeb7486..61ad84d 100644
--- a/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X256Mix.java
+++ b/commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/L64X256Mix.java
@@ -214,7 +214,7 @@
 
     /** {@inheritDoc} */
     @Override
-    protected AbstractL64 copy() {
+    AbstractL64 copy() {
         // This exists to ensure the jump function performed in the super class returns
         // the correct class type. It should not be public.
         return new L64X256Mix(this);