update NEWS.Rd to reflect c++11 detection changes

Author: cauthmann

inst/NEWS.Rd

@@ -7,8 +7,8 @@
     \item Changes in Rcpp API:
     \itemize{
       \item New \code{Rcpp::InternalFunction} interface using
-      \code{std::function}; it needs a \code{define} for \code{RCPP_USE_STD_FUNCTION} 
-      as sufficiently feature-rich C++11 implemented is needed.
+      \code{std::function}; only enabled on compilers that claim full c++11
+      support.
       \item The deprecation of \code{RCPP_FUNCTION_*} which was announced with
       release 0.10.5 last year is proceeding as planned, and the file
       \code{macros/preprocessor_generated.h} has been removed.