Moved findMinMaxPercentile() to rt_algo.*, use bool multiThread in fattal tonemapper, fixes #4195

rtengine/rt_algo.h

@@ -0,0 +1,28 @@
+/*
+ *  This file is part of RawTherapee.
+ *
+ *  Copyright (c) 2017 Ingo Weyrich <heckflosse67@gmx.de>
+ *
+ *  RawTherapee is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  RawTherapee is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with RawTherapee.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <cstddef>
+
+namespace rtengine
+{
+void findMinMaxPercentile (const float *data, size_t size, float minPrct, float& minOut, float maxPrct, float& maxOut, bool multiThread = true);
+
+}