Added Vendor Class Identifier in DHCP offers and requests.

The Vendor Class Identifier is a constant string that identifies the
kind of hardware that asks the DHCP server for a IP address.
The ID is passed via the option 60 of the DHCP messages.

The ID is set to "WIZnetSE" constant.

From a DHCP server point of view, this ID is useful for giving specific
configuration for Wiznet modules : IP address from different address
pool,  different gateway, longer lease, etc.

Reference documentation :
https://datatracker.ietf.org/doc/html/rfc2132#section-9.13

ioLibrary/Internet/DHCP/dhcp.c

@@ -224,6 +224,8 @@ uint32_t DHCP_XID;      // Any number
 
 RIP_MSG* pDHCPMSG;      // Buffer pointer for DHCP processing
 
+uint8_t VENDOR_ID[] = DHCP_VENDOR_ID;
+
 uint8_t HOST_NAME[] = DCHP_HOST_NAME;  
 
 uint8_t DHCP_CHADDR[6] = {0, }; // DHCP Client MAC address.
@@ -387,6 +389,13 @@ void send_DHCP_DISCOVER(void)
 	pDHCPMSG->OPT[k++] = 0x01;
 	pDHCPMSG->OPT[k++] = DHCP_DISCOVER;
 
+	// Class identifier
+	pDHCPMSG->OPT[k++] = dhcpClassIdentifier;
+	pDHCPMSG->OPT[k++] = 0;          // fill zero length of class identifier
+	for(i = 0 ; VENDOR_ID[i] != 0; i++)
+	   	pDHCPMSG->OPT[k++] = VENDOR_ID[i];
+	pDHCPMSG->OPT[k - (i+1)] = i;
+
 	// Client identifier
 	pDHCPMSG->OPT[k++] = dhcpClientIdentifier;
 	pDHCPMSG->OPT[k++] = 0x07;
@@ -476,6 +485,13 @@ void send_DHCP_REQUEST(void)
 	pDHCPMSG->OPT[k++] = 0x01;
 	pDHCPMSG->OPT[k++] = DHCP_REQUEST;
 
+	// Class identifier
+	pDHCPMSG->OPT[k++] = dhcpClassIdentifier;
+	pDHCPMSG->OPT[k++] = 0;          // fill zero length of class identifier
+	for(i = 0 ; VENDOR_ID[i] != 0; i++)
+	   	pDHCPMSG->OPT[k++] = VENDOR_ID[i];
+	pDHCPMSG->OPT[k - (i+1)] = i;
+
 	pDHCPMSG->OPT[k++] = dhcpClientIdentifier;
 	pDHCPMSG->OPT[k++] = 0x07;
 	pDHCPMSG->OPT[k++] = 0x01;

ioLibrary/Internet/DHCP/dhcp.h

@@ -67,6 +67,8 @@
 
 #define MAGIC_COOKIE             0x63825363  ///< Any number. You can be modifyed it any number
 
+#define DHCP_VENDOR_ID           "WIZnetSE"  ///< Vendor ID used for DHCP requests, using Class-Id (option 60)
+
 #define DCHP_HOST_NAME           "WIZnet\0"