Update docs for library configuration

Author: lballabio

Docs/pages/config.docs

@@ -121,6 +121,20 @@
     are used instead of `boost::tuple`. If disabled (the
     default) the Boost facilities are used.
 
+    \code
+    #define QL_USE_STD_ANY
+    \endcode
+    If enabled, `std::any` and related classes and functions will be
+    used instead of `boost::any`. This requires C++17. If disabled
+    (the default) the Boost facilities are used.
+
+    \code
+    #define QL_USE_STD_OPTIONAL
+    \endcode
+    If enabled, `std::optional` and related classes and functions will
+    be used instead of `boost::optional`. This requires C++17. If
+    disabled (the default) the Boost facilities are used.
+
     \code
     #define QL_NULL_AS_FUNCTIONS
     \endcode