Add option to use clew to manually open the OpenCL dynamic library

fix Linux build of App_Bullet3_OpenCL_Demos. Unfortunately the simulation doesn't work properly, need to fix it
(and add unit tests)

test/clew/clewTest.cpp

@@ -0,0 +1,41 @@
+// clewTest.cpp : Defines the entry point for the console application.
+//
+
+#include "clew.h"
+#include <stdio.h>
+
+int main(int argc, char* argv[])
+{
+	int result = -1;
+
+#ifdef _WIN32
+	const char* cl = "OpenCL.dll";
+#elif defined __APPLE__
+	const char* cl = "/System/Library/Frameworks/OpenCL.framework/Versions/Current/OpenCL";
+#else//presumable Linux?
+	//linux (tested on Ubuntu 12.10 with Catalyst 13.4 beta drivers, not that there is no symbolic link from libOpenCL.so
+	const char* cl = "libOpenCL.so.1";
+	result = clewInit(cl);
+	if (result != CLEW_SUCCESS)
+	{
+		cl = "libOpenCL.so";
+	} else
+	{
+		clewExit();
+	}
+#endif
+	result = clewInit(cl);
+	if (result!=CLEW_SUCCESS)
+		printf("clewInit failed with error code %d\n",result);
+	else
+	{
+		printf("clewInit succesfull using %s\n",cl);
+
+		//some test and then
+		clewExit();
+	}
+	
+
+	return 0;
+}
+