Return a pair `(BUFFER . POINT)' pointing to the definition of SYMBOL.
If the definition can't be found in the buffer, return (BUFFER).
TYPE says what type of definition: nil for a function, `defvar' for a
variable, `defface' for a face. This function does not switch to the
buffer nor display it.
The library where SYMBOL is defined is searched for in FILE or
`find-function-source-path', if non-nil, otherwise in `load-path'.
(fn SYMBOL TYPE &optional FILE)