Add msilib documentation.

Doc/lib/lib.tex

@@ -446,6 +446,7 @@ and how to embed it in other applications.
 \input{libsunaudio}
 
 \input{windows}                 % MS Windows ONLY
+\input{libmsilib}
 \input{libmsvcrt}
 \input{libwinreg}
 \input{libwinsound}