Move inline itohex() into header file to allow external access

httpd/page_impl.h

@@ -3,11 +3,26 @@
 
 void send_counters(char port);
 void send_status(void);
-void send_vlan(register uint16_t vlan);
+void send_vlan(uint16_t vlan);
 void send_basic_info(void);
 void send_eee(void);
 void send_mirror(void);
 void send_config(void);
 void send_cmd_log(void);
 
+/*  Convert only the lower nibble to ascii HEX char.
+    For convenience the upper nibble is masked out.
+*/
+inline char itohex(uint8_t val) {
+	// Ignore upper nibble for convenience.
+	val &= 0x0f;
+	val -= 10;
+
+	// 10 or above
+	if ((int8_t)val >= 0)
+		val += ('a' - '0' - 10);
+
+	return val + ('0' + 10);
+}
+
 #endif