package/agentpp: fix build error due to type mismatch

This was supposedly fixed by commit 5f06ecf5e1 ("package/agentpp:
security bump to version 4.6.0") but has kept happening so far.

No public place for contributions, thus this patch has been sent to private
e-mail.

Fixes:
  http://autobuild.buildroot.net/results/e8abd6bdc62a028955915706b03d72239786c703/
  http://autobuild.buildroot.net/results/24441fb679fbf5f913c9b6431c98aec596ead587/

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/agentpp/0001-Snmpx-fix-const-nonconst-type-mismatch.patch

@@ -0,0 +1,51 @@
+From 7e541e6dba8d4976bbb490838a09b569f38b047d Mon Sep 17 00:00:00 2001
+From: Luca Ceresoli <luca.ceresoli@bootlin.com>
+Date: Mon, 26 Jun 2023 17:45:00 +0200
+Subject: [PATCH] Snmpx: fix const/nonconst type mismatch
+
+Fixes build failure:
+
+  snmp_pp_ext.cpp:1176:28: error: binding reference of type 'Snmp_pp::Pdu&' to 'const Snmp_pp::Pdu' discards qualifiers
+   1176 |     status = snmpmsg.load( pdu, community, version);
+        |                            ^~~
+
+Fixes:
+  http://autobuild.buildroot.net/results/e8abd6bdc62a028955915706b03d72239786c703/
+  http://autobuild.buildroot.net/results/24441fb679fbf5f913c9b6431c98aec596ead587/
+
+Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
+Upstream: sent to katz.agentpp.com@magenta.de and support@agentpp.com
+---
+ include/agent_pp/snmp_pp_ext.h | 2 +-
+ src/snmp_pp_ext.cpp            | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/include/agent_pp/snmp_pp_ext.h b/include/agent_pp/snmp_pp_ext.h
+index 7c5a6783ee70..d8a46060db98 100644
+--- a/include/agent_pp/snmp_pp_ext.h
++++ b/include/agent_pp/snmp_pp_ext.h
+@@ -807,7 +807,7 @@ public:
+ 	 *   SNMP_CLASS_SUCCESS on success and SNMP_CLASS_ERROR,
+ 	 *   SNMP_CLASS_TL_FAILED on failure.
+ 	 */
+-        int send (Pdux const &, NS_SNMP UdpAddress const &, NS_SNMP snmp_version, NS_SNMP OctetStr const &);
++        int send (Pdux &, NS_SNMP UdpAddress const &, NS_SNMP snmp_version, NS_SNMP OctetStr const &);
+ #endif
+ 
+ 	/**
+diff --git a/src/snmp_pp_ext.cpp b/src/snmp_pp_ext.cpp
+index 54a29ec8ea28..b61cbf056246 100644
+--- a/src/snmp_pp_ext.cpp
++++ b/src/snmp_pp_ext.cpp
+@@ -1203,7 +1203,7 @@ int Snmpx::send (Pdux &pdu, SnmpTarget* target)
+ 
+ #else  // _SNMPv3 is not defined
+ 
+-int Snmpx::send (Pdux  const &pdu,
++int Snmpx::send (Pdux  &pdu,
+ 		 UdpAddress  const &udp_address,
+ 		 snmp_version version,
+ 		 OctetStr  const &community)
+-- 
+2.34.1
+