(c-end-of-defun-1): Fixed forward scanning into

(c-end-of-defun-1): Fixed forward scanning into
defun block.

(c-auto-newline): Removed this macro since it's
not used anymore.

(c-forward-comment): Removed the workaround
introduced in 5.38 since it had worse side-effects.  If a line
contains the string "//\"", it regarded the // as a comment
start since the \ temporarily doesn't have escape syntax.