nptl needs stdio futexes enabled.

this got reverted in the merge I just did

Signed-off-by: Austin Foxley <austinf@cetoncorp.com>

extra/Configs/Config.in

@@ -435,6 +435,7 @@ config LINUXTHREADS_NEW
 config UCLIBC_HAS_THREADS_NATIVE
 	bool "Native POSIX Threading (NPTL)"
 	select UCLIBC_HAS_TLS
+	select UCLIBC_HAS_STDIO_FUTEXES
 	help
 	  If you want to compile uClibc with NPTL support, then answer Y.