Fix redefinition of make_iterator_range_n in newer versions of Boost

make_iterator_range_n was introduced in Boost 1.56.0
https://github.com/boostorg/range/commit/70256bd8b04036eb9c5db12bc603f84fa8a35541

src/ngx_http_voms_module.cpp

@@ -17,6 +17,7 @@ extern "C" {
 #include <boost/algorithm/string/join.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/optional.hpp>
+#include <boost/version.hpp>
 
 using BioPtr = std::unique_ptr<BIO, decltype(&BIO_free)>;
 using X509Ptr = std::unique_ptr<X509, decltype(&X509_free)>;
@@ -649,6 +650,7 @@ static ngx_int_t get_ssl_client_ee_cert_raw(ngx_http_request_t* r,
   return NGX_OK;
 }
 
+#if BOOST_VERSION < 105600
 namespace boost {
 template <typename IteratorT, typename IntegerT>
 inline iterator_range<IteratorT> make_iterator_range_n(IteratorT first,
@@ -657,6 +659,7 @@ inline iterator_range<IteratorT> make_iterator_range_n(IteratorT first,
   return iterator_range<IteratorT>(first, boost::next(first, n));
 }
 }  // namespace boost
+#endif
 
 static ngx_int_t get_ssl_client_ee_cert(ngx_http_request_t* r,
                                         ngx_http_variable_value_t* v,