Remove MG_ENABLE_STDIO and cleanup

src/fs.c

@@ -0,0 +1,11 @@
+#include "fs.h"
+
+int mg_stat(const char *path, mg_stat_t *st) {
+#ifdef _WIN32
+  wchar_t tmp[MG_PATH_MAX];
+  MultiByteToWideChar(CP_UTF8, 0, path, -1, tmp, sizeof(tmp) / sizeof(tmp[0]));
+  return _wstati64(tmp, st);
+#else
+  return stat(path, st);
+#endif
+}