Description: Fix compilation with -DDEBUG and GDAL >= 2
Author: Even Rouault <even.rouault@spatialys.com>
Origin: https://github.com/libLAS/libLAS/commit/72f7709bf1dfd3473b64cdba0259363d3beea3c3

--- a/src/gt_wkt_srs.cpp
+++ b/src/gt_wkt_srs.cpp
@@ -90,7 +90,11 @@ static const char *papszDatumEquiv[] =
 /*                       LibgeotiffOneTimeInit()                        */
 /************************************************************************/
 
+#if GDAL_VERSION_MAJOR >= 2
+static CPLMutex* hMutex = NULL;
+#else
 static void* hMutex = NULL;
+#endif
 
 void LibgeotiffOneTimeInit() 
 {