function-args.el (moo-tget-scope): rename from `moo-tag-get-scope'
function-args.el (moo-typedefp): return string name or nil
function-args.el (fa-process-tag-according-to-class): fix doc.
function-args.el (moo-dereference-typedef): simplify
function-args.el (moo-tvar->ttype): simplify
function-args.el (fa-calculate): improve x[y].z() case