vim-patch:9.1.0821: 'findexpr' completion doesn't set v:fname to cmdline argument

Problem:  'findexpr' completion doesn't set v:fname to cmdline argument.
Solution: Set v:fname to the cmdline argument as-is (zeertzjq).

closes: vim/vim#15934

20e045f781

src/nvim/eval.h

@@ -167,6 +167,7 @@ typedef enum {
   VV_COLLATE,
   VV_EXITING,
   VV_MAXCOL,
+  VV_CMDCOMPLETE,
   // Nvim
   VV_STDERR,
   VV_MSGPACK_TYPES,