bpo-33164: update blake2 implementation (GH-6286)

diff --git a/configure b/configure
index 72889b9..9f2007f 100755
--- a/configure
+++ b/configure
@@ -11462,14 +11462,14 @@
 
 # checks for library functions
 for ac_func in alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
- clock confstr ctermid dup3 execv faccessat fchmod fchmodat fchown fchownat \
+ clock confstr ctermid dup3 execv explicit_bzero explicit_memset faccessat fchmod fchmodat fchown fchownat \
  fexecve fdopendir fork fpathconf fstatat ftime ftruncate futimesat \
  futimens futimes gai_strerror getentropy \
  getgrgid_r getgrnam_r \
  getgrouplist getgroups getlogin getloadavg getpeername getpgid getpid \
  getpriority getresuid getresgid getpwent getpwnam_r getpwuid_r getspnam getspent getsid getwd \
  if_nameindex \
- initgroups kill killpg lchown lockf linkat lstat lutimes mmap \
+ initgroups kill killpg lchmod lchown lockf linkat lstat lutimes mmap \
  memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
  posix_fallocate posix_fadvise posix_spawn posix_spawnp pread preadv preadv2 \