beginning-of-defun-function and end-of-defun-function go too far

`beginning-of-defun-function` should put cursor in column 0 where the definition begins (currently it puts it at the end of line the line before).

`end-of-defun-function` should put cursor in column 0 after last line of the definition (currently it can go many empty lines below it).

Locate the implementations of beginning-of-defun-function and end-of-defun-function, then inspect how each positions the cursor at definition boundaries. Confirm the behavior with definitions that have preceding or trailing empty lines; done means both functions stop in column 0 at the specified boundary without overshooting.

Written by the indexing model from the issue text.