checkdoc-this-string-valid-engine
checkdoc-this-string-valid-engine is a compiled Lisp function in `checkdoc.el
'.
(checkdoc-this-string-valid-engine FP)
Return an error list or string if the current doc string is invalid.
Depends on `checkdoc-this-string-valid' to reset the syntax table so that
regexp short cuts work. FP is the function defun information.