Updating comments from RcppArmadillo

src/Makevars

@@ -1,5 +1,5 @@
 
-## With R 3.1.0 or later, you can uncomment the following line to tell R to 
+## With R 3.1.0 or later, you can uncomment the following line to tell R to
 ## enable compilation with C++11 (where available)
 ##
 ## Also, OpenMP support in Armadillo prefers C++11 support. However, for wider
@@ -8,6 +8,11 @@
 ##
 ## And with R 3.4.0, and RcppArmadillo 0.7.960.*, we turn C++11 on as OpenMP
 ## support within Armadillo prefers / requires it
+##
+## R 4.0.0 made C++11 the default, R 4.1.0 switched to C++14, R 4.3.0 to C++17
+## _In general_ we should no longer need to set a standard as any recent R
+## installation will do the right thing. Should you need it, uncomment it and
+## set the appropriate value, possibly CXX17.
 CXX_STD = CXX11
 
 PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS) 

src/Makevars.win

@@ -1,5 +1,5 @@
 
-## With R 3.1.0 or later, you can uncomment the following line to tell R to 
+## With R 3.1.0 or later, you can uncomment the following line to tell R to
 ## enable compilation with C++11 (where available)
 ##
 ## Also, OpenMP support in Armadillo prefers C++11 support. However, for wider
@@ -8,6 +8,11 @@
 ##
 ## And with R 3.4.0, and RcppArmadillo 0.7.960.*, we turn C++11 on as OpenMP
 ## support within Armadillo prefers / requires it
+##
+## R 4.0.0 made C++11 the default, R 4.1.0 switched to C++14, R 4.3.0 to C++17
+## _In general_ we should no longer need to set a standard as any recent R
+## installation will do the right thing. Should you need it, uncomment it and
+## set the appropriate value, possibly CXX17.
 CXX_STD = CXX11
 
 PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)