display: use a different color when showing a linting message

This is a second step to address https://savannah.gnu.org/bugs/?54714.

src/nano.h

@@ -153,7 +153,7 @@ typedef enum {
 } file_format;
 
 typedef enum {
-	HUSH, MILD, ALERT
+	HUSH, NOTICE, MILD, ALERT
 } message_type;
 
 typedef enum {

src/text.c

@@ -3265,7 +3265,7 @@ void do_linter(void)
 			confirm_margin();
 #endif
 			edit_refresh();
-			statusbar(curlint->msg);
+			statusline(NOTICE, curlint->msg);
 			bottombars(MLINTER);
 		}
 
@@ -3296,7 +3296,7 @@ void do_linter(void)
 				statusbar(_("At first message"));
 				napms(600);
 				last_wait = time(NULL);
-				statusbar(curlint->msg);
+				statusline(NOTICE, curlint->msg);
 			}
 		} else if (func == do_page_down || func == do_next_block) {
 			if (curlint->next != NULL)
@@ -3305,7 +3305,7 @@ void do_linter(void)
 				statusbar(_("At last message"));
 				napms(600);
 				last_wait = time(NULL);
-				statusbar(curlint->msg);
+				statusline(NOTICE, curlint->msg);
 			}
 		}
 	}

src/winio.c

@@ -2233,7 +2233,9 @@ void statusline(message_type importance, const char *msg, ...)
 		else if (alerts < 4)
 			beep();
 		colorpair = interface_color_pair[ERROR_MESSAGE];
-	} else
+	} else if (importance == NOTICE)
+		colorpair = interface_color_pair[SELECTED_TEXT];
+	else
 		colorpair = interface_color_pair[STATUS_BAR];
 
 	lastmessage = importance;