patch 9.0.1956: Custom completion skips orig cmdline if it invokes glob()

Problem:  Custom cmdline completion skips original cmdline when pressing
          Ctrl-P at first match if completion function invokes glob().
Solution: Move orig_save into struct expand_T.

closes: #13216

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>

src/structs.h

@@ -610,6 +610,7 @@ typedef struct expand
 					// file name completion
     int		xp_col;			// cursor position in line
     int		xp_selected;		// selected index in completion
+    char_u	*xp_orig;		// originally expanded string
     char_u	**xp_files;		// list of files
     char_u	*xp_line;		// text being completed
 #define EXPAND_BUF_LEN 256