[gimp] app: fix indepndent-async thread priority on Windows

[Ell <ell src gnome org>]

commit 190095c97b35b11cffe040b67ea98a6f2fbe2517
Author: Ell <ell_se yahoo com>
Date:   Wed Mar 6 00:06:42 2019 -0500

    app: fix indepndent-async thread priority on Windows
    
    Positive and negative priorities got swapped...

 app/core/gimp-parallel.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/app/core/gimp-parallel.cc b/app/core/gimp-parallel.cc
index aca95fe9a3..ca00f8b01d 100644
--- a/app/core/gimp-parallel.cc
+++ b/app/core/gimp-parallel.cc
@@ -218,11 +218,11 @@ gimp_parallel_run_async_independent_full (gint                     priority,
 #if defined (G_OS_WIN32)
       if (task->priority < 0)
         {
-          SetThreadPriority (GetCurrentThread (), THREAD_MODE_BACKGROUND_BEGIN);
+          SetThreadPriority (GetCurrentThread (), THREAD_MODE_ABOVE_NORMAL);
         }
       else if (task->priority > 0)
         {
-          SetThreadPriority (GetCurrentThread (), THREAD_MODE_ABOVE_NORMAL);
+          SetThreadPriority (GetCurrentThread (), THREAD_MODE_BACKGROUND_BEGIN);
         }
 #elif defined (HAVE_UNISTD_H) && defined (__gnu_linux__)
       if (task->priority)