New documentation for the bdb module. Forward-port from rev. 58112, with a few 3k-specific changes.

Doc/library/debug.rst

+***********************
+Debugging and Profiling
+***********************
+
+These libraries help you with Python development: the debugger enables you to
+step through code, analyze stack frames and set breakpoints etc., and the
+profilers run code and give you a detailed breakdown of execution times,
+allowing you to identify bottlenecks in your programs.
+
+.. toctree::
+
+   bdb.rst
+   pdb.rst
+   profile.rst
+   hotshot.rst
+   timeit.rst
+   trace.rst
\ No newline at end of file

Doc/library/index.rst

@@ -64,11 +64,7 @@ over 2500 additional components available from the `Python Package Index
    frameworks.rst
    tk.rst
    development.rst
-   pdb.rst
-   profile.rst
-   hotshot.rst
-   timeit.rst
-   trace.rst
+   debug.rst
    python.rst
    custominterp.rst
    modules.rst

Doc/library/pdb.rst

 
 .. _debugger:
 
-*******************
-The Python Debugger
-*******************
+:mod:`pdb` --- The Python Debugger
+==================================
 
 .. module:: pdb
    :synopsis: The Python debugger for interactive interpreters.