OpenRTX v0.3.4

Intermediate technical release carrying bugfixes and improvements.

• Implemented the new OpenRTX CPS data format.
• Reorganized and reduced the firmware threads.
• Improved squelch mechanism for M17 mode to avoid random speaker activations in absence of an RF carrier.
• Fixed the oscillation of RF carrier at the first transmission after boot, thanks to Jacob KI5VMF.
• Fixed RX tone squelch bug on MD-UV380.
• Changed UI font from Free Sans to Ubuntu Regular, thanks to edgetriggered.
• Fixed various memory leaks.
• Reorganized linux emulator code.
• Moved to statically allocated framebuffer.
• Implemented linux input stream driver, thanks to Alain.