[BSP] use RT_USING_LIBC instead of RT_USING_NEWLIB

bsp/lpc176x/rtconfig.h

@@ -90,8 +90,8 @@
 // </section>
 
 // <section name="LIBC" description="C Runtime library setting" default="always" >
-// <bool name="RT_USING_NEWLIB" description="Using newlib library, only available under GNU GCC" default="true" />
-// #define RT_USING_NEWLIB
+// <bool name="RT_USING_LIBC" description="Using C library" default="true" />
+// #define RT_USING_LIBC
 // <bool name="RT_USING_PTHREADS" description="Using POSIX threads library" default="true" />
 // #define RT_USING_PTHREADS
 // </section>