Core-M: Import CMSIS-Core(M) 5.5.0 (CMSIS 5.8.0)

This commit imports the CMSIS-Core(M) 5.5.0, which is part of the
CMSIS 5.8.0 release.

Origin: CMSIS_5
License: Apache-2.0
URL: https://github.com/ARM-software/CMSIS_5/tree/5.8.0


commit: 13b9f72f212688d2306d0d085d87cbb4bf9e5d3f
Purpose: Provide a hardware interface to the Arm Cortex-M architecture
Maintained-by: External

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>