Add mp_find_if_q

doc/mp11/algorithm.adoc

@@ -541,6 +541,12 @@ is `mp_size<L>`.
 `mp_find_f<L, P>` is an alias for `mp_size_t<I>`, where `I` is the zero-based index of the first element `T` in `L` for which
 `mp_to_bool<P<T>>` is `mp_true`. If there is no such element, `mp_find_if<L, P>` is `mp_size<L>`.
 
+## mp_find_if_q<L, Q>
+
+    template<class L, class Q> using mp_find_if_q = mp_find_if<L, Q::template fn>;
+
+As `mp_find_if`, but takes a quoted metafunction.
+
 ## mp_reverse<L>
 
     template<class L> using mp_reverse = /*...*/;