[0.96] firmware release suitable for v0.96 hardware - as used on UBSEDS6 and UBSEDS8

There are three issues with this:
* The hardware watchdog cannot be fitted during programming or
  debugging, as it will override the !RESET! line fromt he debug
  probe.
* The ublox GPS may fail to respond after n position requests, where n
  is 1000-10000. Either the firmware should be modified to account for
  this and attempt to reset the GPS, or a watchdog (either hardware or
  software) should be implemented.
* The precision oscillator (TCXO) is connected to the wrong pin on the
  PCB. The output should be connected to PA14 (pin 15) through the
  capacitor and resistor divider as used on later revisions. (See the
  SAMD20 datasheet for more details). Then Line 124 of
  [inc/hw_config.h](inc/hw_config.h) can be uncommented.

Telemetery modes that require precise timing (such as Contestia)
require the TCXO to be connected and used for reliable operation.

firmware/inc/aprs.h

@@ -34,7 +34,7 @@
  *
  * Max. 6 characters
  */
-#define APRS_CALLSIGN	"M0SBU"
+#define APRS_CALLSIGN	"M0"
 #define APRS_SSID	11
 
 /**

firmware/inc/hw_config.h

@@ -121,7 +121,7 @@
 /**
  * XOSC
  */
-#define USE_XOSC
+//#define USE_XOSC /* Uncomment this if TCXO is connected to microcontroller. */
 #define XOSC_FREQUENCY		16369000
 #define XOSC_GCLK1_DIVIDE	4
 

firmware/src/main.c

@@ -52,7 +52,7 @@
 #include "spi_bitbang.h"
 #include "system/interrupt.h"
 
-#define CALLSIGN	"UBSEDS8"
+#define CALLSIGN	"CHANGE"
 
 void xosc_measure_callback(uint32_t result);
 void timepulse_callback(uint32_t sequence);