patch 8.2.4911: the mode #defines are not clearly named

Problem:    The mode #defines are not clearly named.
Solution:   Prepend MODE_.  Renumber them to put the mapped modes first.
diff --git a/src/debugger.c b/src/debugger.c
index 6c38e5a..87cd398 100644
--- a/src/debugger.c
+++ b/src/debugger.c
@@ -88,7 +88,7 @@
     emsg_silent = FALSE;	// display error messages
     redir_off = TRUE;		// don't redirect debug commands
 
-    State = NORMAL;
+    State = MODE_NORMAL;
     debug_mode = TRUE;
 
     if (!debug_did_msg)