Added type gTicks to replace V2.x systemticks_t
Added type gThreadreturn to replace V2.x threadreturn_t
Added type gThreadpriority to replace V2.x threadpriority_t
FEATURE: Added support for operating system initialisation in FreeRTOS
FEATURE: Added GFX_OS_CALL_UGFXMAIN configuration option to allow uGFXMain() to be automatically called
FEATURE: Added GFX_OS_UGFXMAIN_STACKSIZE configuration option to control uGFXMain() stack size