debug first ambe frame
support system image version letters other than 'S'
Revert "debug first ambe frame"

This reverts commit a5f5ae5961d5eae64f82ad5c07ce072a8dbe1df9.
version number experiment
IPv4 moved to callback-based event handling.
Initial support of RP2C
APRS time stamp fixed
Workaround with FreeText over Dextra
Tested version of changed IP stack
RP2C transport layer implemented. Minot fixes to APRS.
Slow Data implementation of phy_send in main.c moved to implementation of slow_data.c
GLONASS support added to APRS
GLONASS support added to GPS
serial ports now use DMA instead of interrupts
send voice+data packets exactly every 20ms to network or phy
fixed buffer overflow bug; sending lots of data (e.g. PHY update) now works
Merge branch 'dl3ock-master' of https://github.com/dl1bff/up4dar-os
RP2C stack are ready to integrate with repeater implementation
new snmp variable for version information
Merge branch 'dl3ock-master' of https://github.com/dl1bff/up4dar-os