v21.02 release

* String routine changes
  * Added AArch64 ILP32 ABI support.
  * Fixed SVE strnlen return value.
  * Added MTE related __mtag_tag_region.
  * Added MTE related __mtag_tag_zero_region.
  * Minor code cleanups.

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 v20.11.
+release is v21.02.
 
 Source code layout: