@hide the bizarro Base64 stream constructors

With no usages of these "backwards" streams, it's not clear that we
want to support them forever in the API.

Also fixed some badly cut-and-pasted javadoc.

Change-Id: I4811d22e493bf2b8eaf79b9e95526e7eab5f27ee

core/java/android/util/base64/Base64InputStream.java

@@ -21,9 +21,8 @@ import java.io.IOException;
 import java.io.InputStream;
 
 /**
- * An OutputStream that does either Base64 encoding or decoding on the
- * data written to it, writing the resulting data to another
- * OutputStream.
+ * An InputStream that does Base64 decoding on the data read through
+ * it.
  */
 public class Base64InputStream extends FilterInputStream {
     private final boolean encode;
@@ -59,6 +58,8 @@ public class Base64InputStream extends FilterInputStream {
      * @param flags bit flags for controlling the decoder; see the
      *        constants in {@link Base64}
      * @param encode true to encode, false to decode
+     *
+     * @hide
      */
     public Base64InputStream(InputStream in, int flags, boolean encode) {
         super(in);

core/java/android/util/base64/Base64OutputStream.java

@@ -21,9 +21,8 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 /**
- * An OutputStream that does either Base64 encoding or decoding on the
- * data written to it, writing the resulting data to another
- * OutputStream.
+ * An OutputStream that does Base64 encoding on the data written to
+ * it, writing the resulting data to another OutputStream.
  */
 public class Base64OutputStream extends FilterOutputStream {
     private final boolean encode;
@@ -57,6 +56,8 @@ public class Base64OutputStream extends FilterOutputStream {
      * @param flags bit flags for controlling the encoder; see the
      *        constants in {@link Base64}
      * @param encode true to encode, false to decode
+     *
+     * @hide
      */
     public Base64OutputStream(OutputStream out, int flags, boolean encode) {
         super(out);