mg(1) make dired-flag-file-deletion file more accurate

[Mark Lumsden]

Instead of just seeing if a line in a dired buffer is longer than 0
before marking it for deletion, check if a filename has the potential
to be extracted from a line. ok? 

-lum

Index: dired.c
===================================================================
RCS file: /cvs/src/usr.bin/mg/dired.c,v
retrieving revision 1.78
diff -u -p -u -p -r1.78 dired.c
--- dired.c     12 Oct 2015 19:08:39 -0000      1.78
+++ dired.c     12 Oct 2015 19:34:50 -0000
@@ -286,7 +286,7 @@ d_del(int f, int n)
        if (n < 0)
                return (FALSE);
        while (n--) {
-               if (llength(curwp->w_dotp) > 0) {
+               if (d_warpdot(curwp->w_dotp, &curwp->w_doto) == TRUE) {
                        lputc(curwp->w_dotp, 0, DDELCHAR);
                        curbp->b_flag |= BFDIREDDEL;
                }