Fix string.h translation with glibc >= 2.43

Author: nunoplopes

cpp2rust/compat/sys/cdefs.h

@@ -0,0 +1,9 @@
+// Copyright (c) 2022-present INESC-ID.
+// Distributed under the MIT license that can be found in the LICENSE file.
+
+#include_next <sys/cdefs.h>
+
+// glibc >= 2.43 wraps strchr, memchr, strstr, etc. in a _Generic selection
+// to preserve the constness of the argument in C23. Disable it so we
+// translate the plain function call.
+#undef __glibc_const_generic