need features.h for the misc attribute defines and uclibc features

ldso/include/dl-string.h

@@ -2,6 +2,7 @@
 #define _LINUX_STRING_H_
 
 #include <dl-sysdep.h> // for do_rem
+#include <features.h>
 
 static size_t _dl_strlen(const char * str);
 static char *_dl_strcat(char *dst, const char *src);