patch 8.0.0641: cannot set a separate highlighting for the quickfix line

Problem:    Cannot set a separate highlighting for the current line in the
            quickfix window.
Solution:   Add QuickFixLine. (anishsane, closes #1755)
diff --git a/src/quickfix.c b/src/quickfix.c
index 8b61e10..61e96dd 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -2575,7 +2575,7 @@
 		vim_snprintf((char *)IObuff, IOSIZE, "%2d %s",
 							    i, (char *)fname);
 	    msg_outtrans_attr(IObuff, i == qi->qf_lists[qi->qf_curlist].qf_index
-					   ? HL_ATTR(HLF_L) : HL_ATTR(HLF_D));
+					   ? HL_ATTR(HLF_QFL) : HL_ATTR(HLF_D));
 	    if (qfp->qf_lnum == 0)
 		IObuff[0] = NUL;
 	    else if (qfp->qf_col == 0)