Make EVP_CIPHER_CTX_copy work in GCM mode.

PR#3272

(Imported from upstream's 14183e50e75f54c44df6be69670180860ac19550 and
802fdcda1ebc4241a8e02af0046ba2f5264f71f6)

Change-Id: Ied6183d938e320f953a18f6616890d88b74def3f
diff --git a/include/openssl/cipher.h b/include/openssl/cipher.h
index 191d44a..19988aa 100644
--- a/include/openssl/cipher.h
+++ b/include/openssl/cipher.h
@@ -325,6 +325,11 @@
  * one. */
 #define EVP_CIPH_FLAG_AEAD_CIPHER 0x800
 
+/* EVP_CIPH_CUSTOM_COPY indicates that the |ctrl| callback should be called
+ * with |EVP_CTRL_COPY| at the end of normal |EVP_CIPHER_CTX_copy|
+ * processing. */
+#define EVP_CIPH_CUSTOM_COPY 0x1000
+
 
 /* Private functions. */