c-backward-single-comment is a compiled Lisp function in `
Move backward past whitespace and the closest preceding comment, if any.
Return t if a comment was found, nil otherwise. In either case, the
point is moved past the preceding whitespace. Line continuations,
i.e. a backslashes followed by line breaks, are treated as whitespace.
The line breaks that end line comments are considered to be the
comment enders, so the point cannot be at the end of the same line to
move over a line comment.
This function does not do any hidden buffer changes.