MSG feature for display.

Thomas dl3el wrote this feature for displaying the the last personal aprs-messages.
    Thomas dl9sau modified: don't overwrite a personal aprs-message with winlink notification.
                            Display shows "m" for personal message. "W" for winlink info. "M" for both.
    Message is cleared when you cycled through the display up to the ((BN)) screen.

    Thomas dl3el's commit messages:
    - include LastMessage in flip pages
      indicate message unread with an "m" between time & uptime
      flag is cleared when all pages have been flipped through and the manual beacon has been sent

    - move display of buildnr to the last butone flip page. Gives us more space for the message "next button will tx beacon"

Signed-off-by: DL3EL <dl3el@darc.de>
Signed-off-by: Thomas Osterried <dl9sau@darc.de>

src/TTGO_T-Beam_LoRa_APRS.ino

@@ -329,7 +329,7 @@ struct LastHeard LH[MAX_LH];
 String RX_RAW_PACKET_LIST[3];
 String LastRXMessage = "";
 String LastRXMessageTimeAndSender = "";
-uint8_t LastRXMessageInfo = 0;  # bitmask: 1 personal aprs text message. 2 winlink message. 3 both. => Display maker: 1: "m", 2: "W", 3: "M"
+uint8_t LastRXMessageInfo = 0;  // bitmask: 1 personal aprs text message. 2 winlink message. 3 both. => Display maker: 1: "m", 2: "W", 3: "M"
 
 //byte Variables
 byte  lora_TXStart;          //start of packet data in TXbuff