minor tweaks, extern templates, fix print_buf

src/c_wrapper/buffer.cpp

src/c_wrapper/buffer.h

src/c_wrapper/clhelper.h

src/c_wrapper/command_queue.cpp

src/c_wrapper/command_queue.h

src/c_wrapper/context.cpp

src/c_wrapper/context.h

src/c_wrapper/device.cpp

src/c_wrapper/device.h

src/c_wrapper/error.h

src/c_wrapper/event.cpp

src/c_wrapper/event.h

src/c_wrapper/gl_obj.cpp

src/c_wrapper/gl_obj.h

src/c_wrapper/image.cpp

src/c_wrapper/image.h

src/c_wrapper/kernel.cpp

src/c_wrapper/kernel.h

src/c_wrapper/memory_map.cpp

src/c_wrapper/memory_map.h