CMSIS-DSP 1.15.0

• Switched to semantic versioning
• Corrections to MFCC
• Updated support for cmsis build tools 2.0
• Compute graph removed. It is now part of CMSIS-Stream
• Github issues:
  • 95,96,105,106,108,111,112
• New FFT initializations to allow linker to do code size optimizations
  • If you know the size of the transform at build time, prefer functions like
    arm_cfft_init_64_q15 to functions like arm_cfft_init_q15.
    It applies for CFFT, RFFT and MFCC and other datatypes.