Log Message:
memcached: updated to 1.6.21

Memcached 1.6.21

Bugfix and community contribution release. As usual most fixes are for the new \ 
proxy code, along with a lot of community contributed tests for proxy.

A data corruption issue for extstore was fixed. Requires overriding item_age to \ 
a low number of seconds and re-writing the same keys frequently.

Fixes a meta protocol ms bug introduced in 1.6.20 with the s flag being returned \ 
when only asking for the c (cas) flag.

Fixes a compilation issue for proxy due to build artifacts being accidentally \ 
included into the release tarball.

Fixes

build: avoid disting build artifacts from vendor/*
extstore: fix data bugs on high overwrite key
proxy: fixes for memory tracking
meta: fix ms c flag reflecting s flag
extstore: fail to start if given no disk space
extstore: Handle incorrect units gracefully
proxy: mcp.internal() support ascii multiget
proxy: fix segfault for reqs with too few tokens
proxy: fix per-worker-thread backend mode batching
proxy: fix meta set M flag for mcp.internal()
proxy: add await tests in proxyunits.t
proxy: add response API tests in proxyunits.t