vim-patch:8.2.1255: cannot use a lambda with quickfix functions

Problem:    Cannot use a lambda with quickfix functions.
Solution:   Add support for lambda. (Yegappan Lakshmanan, closes vim/vim#6499)
d43906d2e5

src/nvim/option.c

@@ -85,6 +85,7 @@
 #include "nvim/api/private/helpers.h"
 #include "nvim/os/input.h"
 #include "nvim/os/lang.h"
+#include "nvim/quickfix.h"
 
 /*
  * The options that are local to a window or buffer have "indir" set to one of
@@ -3182,6 +3183,10 @@ ambw_end:
         }
       }
     }
+  } else if (varp == &p_qftf) {
+    if (!qf_process_qftf_option()) {
+      errmsg = e_invarg;
+    }
   } else {
     // Options that are a list of flags.
     p = NULL;