Add missing deprecations in v1.4 (#7615)

Signed-off-by: José Valim <jose.valim@plataformatec.com.br>

Author: eksperimental

lib/elixir/pages/Compatibility and Deprecations.md

@@ -64,13 +64,15 @@ EEx: `<%=` in middle and end expressions         | [v1.5]        | Use `<%` (= i
 `Float.to_string/2`                              | [v1.4]        | `:erlang.float_to_binary/2` (OTP 17)
 `HashDict` module                                | [v1.4]        | `Map` (v1.2)
 `HashSet` module                                 | [v1.4]        | `MapSet` (v1.1)
+ Multi-letter aliases in `OptionParser`          | [v1.4]        | Use single-letter aliases (v1.0)
 `Set` module                                     | [v1.4]        | `MapSet` (v1.1)
 `Stream.uniq/2`                                  | [v1.4]        | `Stream.uniq_by/2` (v1.2)
 `IEx.Helpers.import_file/2`                      | [v1.4]        | `IEx.Helpers.import_file_if_available/1` (v1.3)
 `Mix.Utils.camelize/1`                           | [v1.4]        | `Macro.camelize/1` (v1.2)
 `Mix.Utils.underscore/1`                         | [v1.4]        | `Macro.underscore/1` (v1.2)
 Variable used as function call                   | [v1.4]        | Use parentheses (v1.0)
 Anonymous functions with no expression after `->` | [v1.4]       | Use an expression or explicitly return `nil` (v1.0)
+Support for making private functions overridable | [v1.4]        | Use public functions (v1.0)
 `Dict` module                                    | [v1.3]        | `Keyword` (v1.0) or `Map` (v1.2)
 `Keyword.size/1`                                 | [v1.3]        | `Kernel.length/1` (v1.0)
 `Map.size/1`                                     | [v1.3]        | `Kernel.map_size/1` (v1.0)