v20.02 release

New functionality
* string: New strrchr and stpcpy routines
* string: New Memory Tagging Extension (MTE) variants of strlen and strchr
* math: New vector version of pow(double)
* networking: Optimized ones' complement checksum for 32-bit and 64-bit Arm

Performance improvements
* string: Improved memcpy and memmove (SIMD and non-SIMD) for 64-bit Arm
* string: Improved memset for 64-bit Arm