relocate android.util.base64.* -> android.util.*

b/2553469 - API REVIEW: android.util.base64

Change-Id: I7b5048a8a6b37cdb437472e759f26b721ad58e3b
diff --git a/core/src/main/java/net/oauth/signature/OAuthSignatureMethod.java b/core/src/main/java/net/oauth/signature/OAuthSignatureMethod.java
index b0384d5..d9da04c 100755
--- a/core/src/main/java/net/oauth/signature/OAuthSignatureMethod.java
+++ b/core/src/main/java/net/oauth/signature/OAuthSignatureMethod.java
@@ -33,7 +33,7 @@
 import net.oauth.OAuthProblemException;
 // BEGIN android-changed
 // import org.apache.commons.codec.binary.Base64;
-import android.util.base64.Base64;
+import android.util.Base64;
 // END android-changed
 
 /**