Improve support for multiple forms in single lines by replacing beginning-of-defun fn

[p4v4n]

This change will improve overall support when multiple forms are present on the same line.

• beginning-of-defun by default moves the cursor to the beginning of line instead of stopping at the opening paren. This can lead to many edge cases when multiple forms are present in the same line.
• To control this behaviour and stop the cursor at opening paren we need use beginning-of-defun-function and beginning-of-defun-raw together.

This change replaces all calls to beginning-of-defun with beginning-of-defun-raw.
(beginning-of-defun-raw calls beginning-of-defun-function internally which in our case is clojure-beginning-of-defun-function)

To see the improvement I have tried M-x cider-eval-defun-at-point(C-c C-c) inside (+ 1 2) in the below example.

(defn f1 [x] (inc x)) (+ 1 2)

(defn f2 [x] (str x))

Before the change the output is #'user/f2. After this change it correctly evaluates to 3.

[bbatsov]

The proposed change looks good to me. Let's just add a couple of unit tests and a changelog entry before we merge it.