Add missing initializer_list constructors to reference docs

doc/unordered/unordered_map.adoc

@@ -69,6 +69,9 @@ namespace boost {
     template<class InputIterator>
       xref:#unordered_map_iterator_range_constructor_with_bucket_count_and_hasher[unordered_map](InputIterator f, InputIterator l, size_type n, const hasher& hf,
                     const allocator_type& a);
+    xref:#unordered_map_initializer_list_constructor_with_bucket_count_and_allocator[unordered_map](std::initializer_list<value_type> il, size_type n, const allocator_type& a);
+    xref:#unordered_map_initializer_list_constructor_with_bucket_count_and_hasher_and_allocator[unordered_map](std::initializer_list<value_type> il, size_type n, const hasher& hf,
+                  const allocator_type& a);
     xref:#unordered_map_destructor[~unordered_map]();
     unordered_map& xref:#unordered_map_copy_assignment[operator++=++](const unordered_map& other);
     unordered_map& xref:#unordered_map_move_assignment[operator++=++](unordered_map&& other)
@@ -550,6 +553,33 @@ Requires:;; `key_equal` needs to be https://en.cppreference.com/w/cpp/named_req/
 
 ---
 
+==== initializer_list Constructor with Bucket Count and Allocator
+
+```c++
+unordered_map(std::initializer_list<value_type> il, size_type n, const allocator_type& a);
+```
+
+Constructs an empty container with at least `n` buckets, using `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.
+
+[horizontal]
+Requires:;; `hasher` and `key_equal` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
+
+---
+
+==== initializer_list Constructor with Bucket Count and Hasher and Allocator
+
+```c++
+unordered_map(std::initializer_list<value_type> il, size_type n, const hasher& hf,
+              const allocator_type& a);
+```
+
+Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `a` as the allocator and a maximum load factor of 1.0 and inserts the elements from `il` into it.
+
+[horizontal]
+Requires:;; `key_equal` needs to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
+
+---
+
 === Destructor
 
 ```c++