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/window.c b/src/window.c
index fc00403..b4f8c1d 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2259,7 +2259,7 @@
     // When leaving the window (or closing the window) was done from a
     // callback we need to break out of the Insert mode loop and restart Insert
     // mode when entering the window again.
-    if (State & INSERT)
+    if (State & MODE_INSERT)
     {
 	stop_insert_mode = TRUE;
 	if (win->w_buffer->b_prompt_insert == NUL)
@@ -2281,7 +2281,7 @@
 
     // When entering the prompt window restart Insert mode if we were in Insert
     // mode when we left it and not already in Insert mode.
-    if ((State & INSERT) == 0)
+    if ((State & MODE_INSERT) == 0)
 	restart_edit = win->w_buffer->b_prompt_insert;
 }
 #endif