APRS address and routing fix. (#77)

* Update config.h

Added note to APRS_RELAYS line.

* Update ax25.h

source_ssid and destination_ssid did not match. Uint8_t was used in function definition within ax25.c file. Now all should match.

* Update ax25.c

source_ssid and destination_ssid are both defined the same in config.h and in ax25.h.  Both are inserted to memory by adjusting a pointer. Therefore both should require moving the pointer back 7 bytes to place in correctly addressed position. I am puzzled that the header definition and the cast in this code line are both needed.

src/codecs/ax25/ax25.c

@@ -89,7 +89,7 @@ uint16_t ax25_encode_packet_aprs(char *source, uint8_t source_ssid, char *destin
     call_length = strlen(destination);
     memset(header->destination, ' ', sizeof(header->destination));
     memcpy(header->destination, destination, call_length < 6 ? call_length : 6);
-    header->destination_ssid = destination_ssid;
+    header->destination_ssid = (uint8_t) destination_ssid >= 'A' ? destination_ssid - 7 : destination_ssid);;
 
     char *digipeater_addresses_start = ((char *) header) + 1 + 14;
     uint16_t digipeater_addresses_length = ax25_encode_digipeater_path(digipeater_addresses, digipeater_addresses_start);

src/codecs/ax25/ax25.h

@@ -13,7 +13,7 @@ typedef struct _ax25_packet_header {
     char destination[6];
     uint8_t destination_ssid;
     char source[6];
-    char source_ssid;
+    uint8_t source_ssid;
 } ax25_packet_header;
 
 typedef struct _ax25_packet_header_end {

src/config.h

@@ -275,7 +275,7 @@
 #define APRS_SYMBOL_TABLE '/' // '/' denotes primary and '\\' denotes alternate APRS symbol table
 #define APRS_SYMBOL 'O'
 #define APRS_COMMENT "RS41ng radiosonde firmware test"
-#define APRS_RELAYS "WIDE1-1,WIDE2-1"
+#define APRS_RELAYS "WIDE1-1,WIDE2-1"   //Do not include any spaces in the APRS_RELAYS
 #define APRS_DESTINATION "APZ41N"
 #define APRS_DESTINATION_SSID '0'
 // Generate an APRS weather report instead of a position report. This will override the APRS symbol with the weather station symbol.