CC Mode: Fix bug #39972, by fixing c-display-defun-name for nested defuns
* lisp/progmodes/cc-mode.el (c-common-init): Build add-log-current-defun-function out of c-defun-name-and-limits instead of the former c-defun-name.
* lisp/progmodes/cc-mode.el (c-common-init): Build add-log-current-defun-function out of c-defun-name-and-limits instead of the former c-defun-name.