_getframe(): New sys module function for getting at the stack frame.
Implements and closes SF patch #102106, with Guido's suggested
documentation changes.
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 8199b1b..2fda26e 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -161,6 +161,17 @@
be set by \function{setrecursionlimit()}.
\end{funcdesc}
+\begin{funcdesc}{_getframe}{\optional{depth}}
+Return a frame object from the call stack. If optional integer
+\var{depth} is given, return the frame object that many calls below
+the top of the stack. If that is deeper than the call stack,
+\exception{ValueError} is raised. The default for \var{depth} is
+zero, returning the frame at the top of the call stack.
+
+This function should be used for internal and specialized
+purposes only.
+\end{funcdesc}
+
\begin{datadesc}{hexversion}
The version number encoded as a single integer. This is guaranteed to
increase with each version, including proper support for