patch 8.0.0590: cannot add a context to locations

Problem:    Cannot add a context to locations.
Solution:   Add the "context" entry in location entries. (Yegappan Lakshmanan,
            closes #1012)
diff --git a/src/eval.c b/src/eval.c
index 5f589eb..1313cef 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -5327,6 +5327,10 @@
     abort = abort || set_ref_in_timer(copyID);
 #endif
 
+#ifdef FEAT_QUICKFIX
+    abort = abort || set_ref_in_quickfix(copyID);
+#endif
+
     if (!abort)
     {
 	/*