Partial backport of:

commit 6781d8e693eb9e1251875222db5c9885d7ebb596
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Jun 30 11:31:41 2017 +0200

    resolv: Turn _res_opcodes into a compatibility symbol

The backport avoids depending on the GLIBC_2.26 symbol version.

diff --git a/include/resolv.h b/include/resolv.h
index 4d5b51e873ad62a1..2938506d75ee5d43 100644
--- a/include/resolv.h
+++ b/include/resolv.h
@@ -90,8 +90,5 @@ libresolv_hidden_proto (__b64_ntop)
 libresolv_hidden_proto (__dn_count_labels)
 libresolv_hidden_proto (__p_secstodate)
 
-extern const char *_res_opcodes[];
-libresolv_hidden_proto (_res_opcodes)
-
 # endif /* _RESOLV_H_ && !_ISOMAC */
 #endif
diff --git a/resolv/res_debug.c b/resolv/res_debug.c
index 182aeefa1f8683f4..b26c38bae0a1674b 100644
--- a/resolv/res_debug.c
+++ b/resolv/res_debug.c
@@ -106,6 +106,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <shlib-compat.h>
 
 #ifdef SPRINTF_CHAR
 # define SPRINTF(x) strlen(sprintf/**/x)
@@ -115,7 +116,8 @@
 
 extern const char *_res_sectioncodes[] attribute_hidden;
 
-const char *_res_opcodes[] =
+/* _res_opcodes was exported by accident as a variable.  */
+static const char *res_opcodes[] =
   {
     "QUERY",
     "IQUERY",
@@ -134,7 +136,7 @@ const char *_res_opcodes[] =
     "ZONEINIT",
     "ZONEREF",
   };
-libresolv_hidden_data_def (_res_opcodes)
+strong_alias (res_opcodes, _res_opcodes)
 
 static const char *p_section(int section, int opcode);
 
@@ -259,7 +261,7 @@ fp_nquery (const unsigned char *msg, int len, FILE *file)
 	if ((!pfcode) || (pfcode & RES_PRF_HEADX) || rcode)
 		fprintf(file,
 			";; ->>HEADER<<- opcode: %s, status: %s, id: %d\n",
-			_res_opcodes[opcode], p_rcode(rcode), id);
+			res_opcodes[opcode], p_rcode(rcode), id);
 	if ((!pfcode) || (pfcode & RES_PRF_HEADX))
 		putc(';', file);
 	if ((!pfcode) || (pfcode & RES_PRF_HEAD2)) {