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/screen.c b/src/screen.c
index 325d9ae..f10f70d 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -3371,7 +3371,7 @@
 # if defined(FEAT_QUICKFIX) && defined(FEAT_WINDOWS)
     /* Highlight the current line in the quickfix window. */
     if (bt_quickfix(wp->w_buffer) && qf_current_entry(wp) == lnum)
-	line_attr = HL_ATTR(HLF_L);
+	line_attr = HL_ATTR(HLF_QFL);
 # endif
     if (line_attr != 0)
 	area_highlighting = TRUE;