v20.05 release

* New functionality (64-bit Arm)
  * string: Optimized MTE variants of strlen, strnlen, strchr,
    strchrnul, strrchr, memchr, memrchr, strcpy, stpcpy, strcmp,
    strncmp
  * string: Changes to support BTI
  * string: New optimized memrchr, strnlen
* Performance improvements (Neoverse N1)
  * strchr/strchrnul: 21% improvement on long strings
  * strrchr: 11% improvement
  * strnlen: 130% improvement on long strings, 50% on short strings
* Benchmark and tests
  * string: New memcpy benchmark
  * string: Cleanup testsuite and improve test coverage

Author: nsz-arm

README

@@ -9,7 +9,7 @@ contributor-agreement.pdf. This is needed so upstreaming code
 to projects that require copyright assignment is possible.
 
 Regular quarterly releases are tagged as vYY.MM, the latest
-release is v20.02.
+release is v20.05.
 
 Source code layout: