Correct header for size_t (#454)

* Correct header for size_t

* Be consistent with using C++ specific C compat headers

* NEWS bullet

---------

Co-authored-by: Davis Vaughan <davis@posit.co>

Author: MichaelChirico

NEWS.md

@@ -1,5 +1,7 @@
 # cpp11 (development version)
 
+* Improved hygiene around using C++ specific C compatibility headers (i.e. by using `<cstring>` rather than `<string.h>` and `<cstddef>` rather than `<stddef.h>`) (#454, @MichaelChirico).
+
 * Fixed an rchk issue related to `std::initializer_list<named_arg>` (#457, @pachadotdev).
 
 # cpp11 0.5.2

inst/include/cpp11/function.hpp

@@ -1,8 +1,7 @@
 #pragma once
 
-#include <string.h>  // for strcmp
-
 #include <cstdio>   // for snprintf
+#include <cstring>  // for strcmp
 #include <string>   // for string, basic_string
 #include <utility>  // for forward
 

inst/include/cpp11/named_arg.hpp

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <stddef.h>  // for size_t
+#include <cstddef>  // for size_t
 
 #include <initializer_list>  // for initializer_list
 

inst/include/cpp11/r_vector.hpp

@@ -1,9 +1,8 @@
 #pragma once
 
-#include <stddef.h>  // for ptrdiff_t, size_t
-
 #include <algorithm>         // for max
 #include <array>             // for array
+#include <cstddef>           // for ptrdiff_t, size_t
 #include <cstdio>            // for snprintf
 #include <cstring>           // for memcpy
 #include <exception>         // for exception

inst/include/cpp11/sexp.hpp

@@ -1,8 +1,7 @@
 #pragma once
 
-#include <stddef.h>  // for size_t
-
-#include <string>  // for string, basic_string
+#include <cstddef>  // for size_t
+#include <string>   // for string, basic_string
 
 #include "cpp11/R.hpp"                // for SEXP, SEXPREC, REAL_ELT, R_NilV...
 #include "cpp11/attribute_proxy.hpp"  // for attribute_proxy