Log Message:
memcached: updated to 1.5.21

Memcached 1.5.21

Overview
Bugfixes and smaller changes. Thanks to all the external contributors!

Fixes
Adding missing defaults to the --help output
stats: Fix stats delimiter unit tests
Allow compilation with ASAN
restart: add error handling if mmap fails
For text auth token mode, use alternative bcmp implementation
memcached-tool: Fix up tabular output for the 'stats' command.
linux_priv.c: add termios.h include to fix powerpc(64) builds
Update the build documentation in BUILD file
Update documentation for --max-item-size
Fix build issue due to improper pthread_t comparison
Ensure t/whitespace.t test is skipped when outside a memcached git checkout
Allocating large chunk of slabs for FreeBSD.

New Features
configuration option to disable watch commands (-W)