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/indent.c b/src/indent.c
index e8892b5..0666f0e 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -828,7 +828,7 @@
     pos.lnum = 0;
 
     // In format_lines() (i.e. not insert mode), fo+=q is needed too...
-    if ((State & INSERT) || has_format_option(FO_Q_COMS))
+    if ((State & MODE_INSERT) || has_format_option(FO_Q_COMS))
 	lead_len = get_leader_len(ml_get(lnum), NULL, FALSE, TRUE);
 
     regmatch.regprog = vim_regcomp(curbuf->b_p_flp, RE_MAGIC);
@@ -1276,7 +1276,7 @@
     colnr_T	orig_col = 0;		// init for GCC
     char_u	*new_line, *orig_line = NULL;	// init for GCC
 
-    // VREPLACE mode needs to know what the line was like before changing
+    // MODE_VREPLACE state needs to know what the line was like before changing
     if (State & VREPLACE_FLAG)
     {
 	orig_line = vim_strsave(ml_get_curline());  // Deal with NULL below
@@ -1318,7 +1318,7 @@
 
 	// Avoid being called recursively.
 	if (State & VREPLACE_FLAG)
-	    State = INSERT;
+	    State = MODE_INSERT;
 	shift_line(type == INDENT_DEC, round, 1, call_changed_bytes);
 	State = save_State;
     }
@@ -1339,7 +1339,7 @@
 	    insstart_less = MAXCOL;
 	new_cursor_col += curwin->w_cursor.col;
     }
-    else if (!(State & INSERT))
+    else if (!(State & MODE_INSERT))
 	new_cursor_col = curwin->w_cursor.col;
     else
     {
@@ -1397,7 +1397,7 @@
     changed_cline_bef_curs();
 
     // May have to adjust the start of the insert.
-    if (State & INSERT)
+    if (State & MODE_INSERT)
     {
 	if (curwin->w_cursor.lnum == Insstart.lnum && Insstart.col != 0)
 	{
@@ -1412,9 +1412,9 @@
 	    ai_col -= insstart_less;
     }
 
-    // For REPLACE mode, may have to fix the replace stack, if it's possible.
-    // If the number of characters before the cursor decreased, need to pop a
-    // few characters from the replace stack.
+    // For MODE_REPLACE state, may have to fix the replace stack, if it's
+    // possible.  If the number of characters before the cursor decreased, need
+    // to pop a few characters from the replace stack.
     // If the number of characters before the cursor increased, need to push a
     // few NULs onto the replace stack.
     if (REPLACE_NORMAL(State) && start_col >= 0)
@@ -1436,9 +1436,9 @@
 	}
     }
 
-    // For VREPLACE mode, we also have to fix the replace stack.  In this case
-    // it is always possible because we backspace over the whole line and then
-    // put it back again the way we wanted it.
+    // For MODE_VREPLACE state, we also have to fix the replace stack.  In this
+    // case it is always possible because we backspace over the whole line and
+    // then put it back again the way we wanted it.
     if (State & VREPLACE_FLAG)
     {
 	// If orig_line didn't allocate, just return.  At least we did the job,
@@ -1894,7 +1894,7 @@
     // Pretend to be in Insert mode, allow cursor past end of line for "o"
     // command.
     save_State = State;
-    State = INSERT;
+    State = MODE_INSERT;
     curwin->w_cursor = save_pos;
     curwin->w_curswant = save_curswant;
     curwin->w_set_curswant = save_set_curswant;