readme: Provide a GLEW_KHR_debug example instead of GLEW_GREMEDY_string_marker.

[apitrace] / wrappers / dwritetrace.cpp

#include <windows.h>

EXTERN_C BOOL WINAPI
DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
    return TRUE;
}