help-add-fundoc-usage
help-add-fundoc-usage is a compiled Lisp function in `help.el
'.
(help-add-fundoc-usage DOCSTRING ARGLIST)
Add the usage info to DOCSTRING.
If DOCSTRING already has a usage info, then just return it unchanged.
The usage info is built from ARGLIST. DOCSTRING can be nil.
ARGLIST can also be t or a string of the form "(FUN ARG1 ARG2 ...)".