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/message.c b/src/message.c
index 4264121..8c8e954 100644
--- a/src/message.c
+++ b/src/message.c
@@ -2319,10 +2319,10 @@
 {
     int match;
 
-    if (cmdmod.filter_regmatch.regprog == NULL)
+    if (cmdmod.cmod_filter_regmatch.regprog == NULL)
 	return FALSE;
-    match = vim_regexec(&cmdmod.filter_regmatch, msg, (colnr_T)0);
-    return cmdmod.filter_force ? match : !match;
+    match = vim_regexec(&cmdmod.cmod_filter_regmatch, msg, (colnr_T)0);
+    return cmdmod.cmod_filter_force ? match : !match;
 }
 
 /*