Documentation for ctypes.

I think that 'generic operating system services' is the best category.
Note that the Doc/lib/libctypes.latex file is generated from reST sources.
You are welcome to make typo fixes, and I'll try to keep the reST sources
in sync, but markup changes would be lost - they should be fixed in the tool
that creates the latex file.
The conversion script is external/ctypes/docs/manual/mkpydoc.py.

Doc/lib/lib.tex

@@ -243,6 +243,7 @@ and how to embed it in other applications.
 \input{libcursespanel}
 \input{libplatform}
 \input{liberrno}
+\input{libctypes}
 
 \input{libsomeos}               % Optional Operating System Services
 \input{libselect}