sync: always send mailbox annotations
annotations: handle missing userid (FastMail bug in make_key)
dlist: use non-literals where legit
xstrdupnull for annotations
annotate.c: init userid regardless
annotate: skip an extra memcpy
sync: tidying annot codepaths
util: strcmpnull - NULL isn't ""
sync: support NULL userid for annotations
dlist: allow NIL atoms
dlist: don't forget to protect from nothingness!
annotate check for bogus entries
more detail, bah
annotate: extract userid correctly (fixes broken specialuse)