patch 8.2.1898: command modifier parsing always uses global cmdmod

Problem:    Command modifier parsing always uses global cmdmod.
Solution:   Pass in cmdmod_T to use.  Rename struct fields consistently.
diff --git a/src/edit.c b/src/edit.c
index 14a21d9..73e8337 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -3616,7 +3616,7 @@
 	curwin->w_set_curswant = TRUE;
 
     // Remember the last Insert position in the '^ mark.
-    if (!cmdmod.keepjumps)
+    if ((cmdmod.cmod_flags & CMOD_KEEPJUMPS) == 0)
 	curbuf->b_last_insert = curwin->w_cursor;
 
     /*