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/if_cscope.c b/src/if_cscope.c
index c027c71..bbb429a 100644
--- a/src/if_cscope.c
+++ b/src/if_cscope.c
@@ -212,8 +212,8 @@
 	    return;
 	}
 	postponed_split = -1;
-	postponed_split_flags = cmdmod.split;
-	postponed_split_tab = cmdmod.tab;
+	postponed_split_flags = cmdmod.cmod_split;
+	postponed_split_tab = cmdmod.cmod_tab;
     }
 
     cmdp->func(eap);