Issue #14605: Rename _SourcelessFileLoader to SourcelessFileLoader.

This time also recreating the Python/importlib.h file to make
make happy. See the ticket for details.
diff --git a/Doc/library/importlib.rst b/Doc/library/importlib.rst
index de29e4f..a8013d2 100644
--- a/Doc/library/importlib.rst
+++ b/Doc/library/importlib.rst
@@ -606,18 +606,15 @@
       Load the specified module if it is the same as :attr:`name`.
 
 
-.. class:: _SourcelessFileLoader(fullname, path)
+.. class:: SourcelessFileLoader(fullname, path)
 
    A concrete implementation of :class:`importlib.abc.FileLoader` which can
    import bytecode files (i.e. no source code files exist).
 
-   It is **strongly** suggested you do not rely on this loader (hence the
-   leading underscore of the class). Direct use of bytecode files (and thus not
-   source code files) inhibits your modules from being usable by all Python
-   implementations. It also runs the risk of your bytecode files not being
-   usable by new versions of Python which change the bytecode format. This
-   class is only documented as it is directly used by import and thus can
-   potentially have instances show up as a module's ``__loader__`` attribute.
+   Please note that direct use of bytecode files (and thus not source code
+   files) inhibits your modules from being usable by all Python
+   implementations or new versions of Python which change the bytecode
+   format.
 
    .. versionadded:: 3.3