Initial checkin of docs for Lib/platform.py .
Closes patch #785752 and bug #726911.

Should be backported after correctness and such has been verified by Fred.
diff --git a/Doc/lib/lib.tex b/Doc/lib/lib.tex
index 4d71d93..c8cb73b 100644
--- a/Doc/lib/lib.tex
+++ b/Doc/lib/lib.tex
@@ -163,6 +163,7 @@
 \input{liblocale}
 \input{libgettext}
 \input{liblogging}
+\input{libplatform}
 
 \input{libsomeos}               % Optional Operating System Services
 \input{libsignal}