bug#17218: 24.3; Dired does not insert subdirs when used with switch "--group-directories-first"

[Drew Adams]

> I found out the problem in the function "dired-insert-old-subdirs"
> at line 1367 in dired.el.

There is a similar problem in `dired-sort-R-check' and
`dired-build-subdir-alist'.

[There probably should be a function that checks for a given switch, and does 
not just use `string-match-p' in such a simple way.  (At least it should 
respect case etc.)]