Add a hint that CSD == Service Pack.

People searcing for the way to get a "service pack" will never find that we
provide it here, and people that find this function won't know what CSD is
until they run the function. On top of this, they won't know what the value
means unless they really have a service pack installed.

CSD, or Customer Service Diagnostics, is apparently no longer used, and was
rarely used term at that. Most references to it online are from
universities making Windows 2000 and XP service packs available to students.

Doc/library/platform.rst

@@ -188,8 +188,8 @@ Windows Platform
 .. function:: win32_ver(release='', version='', csd='', ptype='')
 
    Get additional version information from the Windows Registry and return a tuple
-   ``(version, csd, ptype)`` referring to version number, CSD level and OS type
-   (multi/single processor).
+   ``(version, csd, ptype)`` referring to version number, CSD level
+   (service pack) and OS type (multi/single processor).
 
    As a hint: *ptype* is ``'Uniprocessor Free'`` on single processor NT machines
    and ``'Multiprocessor Free'`` on multi processor machines. The *'Free'* refers

Lib/platform.py

@@ -549,7 +549,7 @@ def win32_ver(release='',version='',csd='',ptype=''):
 
     """ Get additional version information from the Windows Registry
         and return a tuple (version,csd,ptype) referring to version
-        number, CSD level and OS type (multi/single
+        number, CSD level (service pack), and OS type (multi/single
         processor).
 
         As a hint: ptype returns 'Uniprocessor Free' on single