dhcpserver: support cplusplus

Closes https://github.com/espressif/esp-idf/issues/7494

Merges https://github.com/espressif/esp-idf/pull/7526

components/lwip/include/apps/dhcpserver/dhcpserver.h

@@ -17,6 +17,10 @@
 #include "sdkconfig.h"
 #include "lwip/ip_addr.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 typedef struct dhcps_state{
         s16_t state;
 } dhcps_state;
@@ -91,4 +95,8 @@ void dhcps_dns_setserver(const ip_addr_t *dnsserver);
 ip4_addr_t dhcps_dns_getserver(void);
 void dhcps_set_new_lease_cb(dhcps_cb_t cb);
 
+#ifdef __cplusplus
+}
 #endif
+
+#endif /* __DHCPS_H__ */

components/lwip/include/apps/dhcpserver/dhcpserver_options.h

@@ -13,6 +13,9 @@
 // limitations under the License.
 #pragma once
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 /** DHCP Options
 
     This macros are not part of the public dhcpserver.h interface.
@@ -132,3 +135,7 @@ typedef enum
     DOMAIN_SEARCH = 119,
     CLASSLESS_ROUTE = 121,
 } dhcp_msg_option;
+
+#ifdef __cplusplus
+}
+#endif