patch 9.0.1735: Rename completion specific findex var

Problem: Rename completion specific findex var
Solution: Move "findex" static variable to xp_selected in expand_T

closes: #12548

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/structs.h b/src/structs.h
index 1b4308e..d8c6aef 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -609,6 +609,7 @@
     int		xp_numfiles;		// number of files found by
 					// file name completion
     int		xp_col;			// cursor position in line
+    int		xp_selected;		// selected index in completion
     char_u	**xp_files;		// list of files
     char_u	*xp_line;		// text being completed
 #define EXPAND_BUF_LEN 256