CMSIS-Compiler

      Changes since CMSIS-Compiler 2.1.0:
      - Add components that enable stdio retarget to UART
      - Update example project
      AC6:
      - correct _sys_read return value when rt_fs_read returns with error
      - correct _mutex_initialize to check whether RTOS2 kernel is initialized
      IAR:
      - add support for multithreading
      - add support for file redirection

      - AC6: correct _sys_open handling for OPEN_A, file is created if non-existent (#50)
      - GCC: add missing forward declarations for retargeted functions (#51, #53)
      - Add Cortex-M52 support
      - GCC: Disable heap limit check in _sbrk_r implementation (#54)

      - Added initial support for LLVM/Clang and IAR Compiler
      - Introduce STDERR, STDIN, STDOUT APIs and components
        Attention: This change conflicts with user implementations version 1.0.0!
      - Rename RTE component defines from RTE_Compiler_* to RTE_CMSIS_Compiler_*
      - OS Interface, Arm Compiler: Remove C library thread space implementation

      Initial release replacing I/O Retarget from Keil.ARM-Compiler pack.