patch from IRIE Shinsuke, use systems openjpeg on *nix.

CMakeLists.txt

@@ -933,8 +933,15 @@ if(WITH_RAYOPTIMIZATION)
 endif()
 
 if(WITH_IMAGE_OPENJPEG)
-	set(OPENJPEG ${CMAKE_SOURCE_DIR}/extern/libopenjpeg)
-	set(OPENJPEG_INC ${OPENJPEG})
+	if(UNIX AND NOT APPLE)
+		set(OPENJPEG /usr)
+		set(OPENJPEG_INC ${OPENJPEG}/include)
+		set(OPENJPEG_LIB openjpeg)
+		set(OPENJPEG_LIBPATH ${OPENJPEG}/lib)
+	else()
+		set(OPENJPEG ${CMAKE_SOURCE_DIR}/extern/libopenjpeg)
+		set(OPENJPEG_INC ${OPENJPEG})
+	endif()
 endif()
 
 if(WITH_IMAGE_REDCODE)