Remove is_first_nonwhitespace_on_line(), instead improve get_visual_column()

Remove is_first_nonwhitespace_on_line(), instead improve get_visual_column()

gcc/c-family/ChangeLog:

	* c-indentation.c (get_visual_column): Add parameter first_nws,
	use it.  Update comment documenting the function.
	(is_first_nonwhitespace_on_line): Remove.
	(should_warn_for_misleading_indentation): Replace usage of
	of is_first_nonwhitespace_on_line with get_visual_column.

From-SVN: r226478