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/ex_docmd.c b/src/ex_docmd.c
index 46f2b22..7633d6b 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -476,7 +476,7 @@
 	exmode_active = EXMODE_VIM;
     else
 	exmode_active = EXMODE_NORMAL;
-    State = NORMAL;
+    State = MODE_NORMAL;
     may_trigger_modechanged();
 
     // When using ":global /pat/ visual" and then "Q" we return to continue
@@ -8328,7 +8328,7 @@
     need_wait_return = FALSE;
 
     // When invoked from a callback or autocmd the command line may be active.
-    if (State & CMDLINE)
+    if (State & MODE_CMDLINE)
 	redrawcmdline();
 
     out_flush();
@@ -8676,7 +8676,7 @@
 
     // Ignore the command when already in Insert mode.  Inserting an
     // expression register that invokes a function can do this.
-    if (State & INSERT)
+    if (State & MODE_INSERT)
 	return;
 
     if (eap->cmdidx == CMD_startinsert)