Add source links to documentation for Windows-specific modules (GH-130244)

Doc/library/msvcrt.rst

@@ -7,6 +7,8 @@
 
 .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
 
+**Source code:** :source:`PC/msvcrtmodule.c`
+
 --------------
 
 These functions provide access to some useful capabilities on Windows platforms.

Doc/library/winreg.rst

@@ -7,6 +7,8 @@
 
 .. sectionauthor:: Mark Hammond <MarkH@ActiveState.com>
 
+**Source code:** :source:`PC/winreg.c`
+
 --------------
 
 These functions expose the Windows registry API to Python.  Instead of using an
@@ -25,7 +27,7 @@ to explicitly close them.
 .. _functions:
 
 Functions
-------------------
+---------
 
 This module offers the following functions:
 
@@ -554,7 +556,7 @@ This module offers the following functions:
 .. _constants:
 
 Constants
-------------------
+---------
 
 The following constants are defined for use in many :mod:`winreg` functions.
 

Doc/library/winsound.rst

@@ -8,6 +8,8 @@
 .. moduleauthor:: Toby Dickenson <htrd90@zepler.org>
 .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
 
+**Source code:** :source:`PC/winsound.c`
+
 --------------
 
 The :mod:`winsound` module provides access to the basic sound-playing machinery
@@ -16,6 +18,9 @@ provided by Windows platforms.  It includes functions and several constants.
 .. availability:: Windows.
 
 
+Functions
+---------
+
 .. function:: Beep(frequency, duration)
 
    Beep the PC's speaker. The *frequency* parameter specifies frequency, in hertz,
@@ -46,6 +51,9 @@ provided by Windows platforms.  It includes functions and several constants.
    error, :exc:`RuntimeError` is raised.
 
 
+Constants
+---------
+
 .. data:: SND_FILENAME
 
    The *sound* parameter is the name of a WAV file. Do not use with