patch 8.2.5129: timeout handling is not optimal

Problem:    Timeout handling is not optimal.
Solution:   Avoid setting timeout_flag twice.  Adjust the pointer when
            stopping the regexp timeout.  Adjust variable name.
diff --git a/src/os_win32.c b/src/os_win32.c
index 1adaaed..f325935 100644
--- a/src/os_win32.c
+++ b/src/os_win32.c
@@ -8335,7 +8335,7 @@
  * timeouts.
  */
 static int      timeout_flags[2];
-static int      flag_idx = 0;
+static int      timeout_flag_idx = 0;
 static int      *timeout_flag = &timeout_flags[0];
 
 
@@ -8383,7 +8383,7 @@
 {
     BOOL ret;
 
-    timeout_flag = &timeout_flags[flag_idx];
+    timeout_flag = &timeout_flags[timeout_flag_idx];
 
     stop_timeout();
     ret = CreateTimerQueueTimer(
@@ -8395,7 +8395,7 @@
     }
     else
     {
-	flag_idx = (flag_idx + 1) % 2;
+	timeout_flag_idx = (timeout_flag_idx + 1) % 2;
 	timer_active = TRUE;
 	*timeout_flag = FALSE;
     }