Update docstring and library reference section on 'sys' module.
New API PyErr_Display, just for displaying errors, called by excepthook.
Uncaught exceptions now call sys.excepthook; if that fails, we fall back
    to calling PyErr_Display directly.
Also comes with sys.__excepthook__ and sys.__displayhook__.

If a module has a future statement enabling nested scopes, they are
also enable for the exec statement and the functions compile() and
execfile() if they occur in the module.

If Python is run with the -i option, which enters interactive mode
after executing a script, and the script it runs enables nested
scopes, they are also enabled in interactive mode.

XXX The use of -i with -c "from __future__ import nested_scopes" is
not supported.  What's the point?

To support these changes, many function variants have been added to
pythonrun.c.  All the variants names end with Flags and they take an
extra PyCompilerFlags * argument.  It is possible that this complexity
will be eliminated in a future version of the interpreter in which
nested scopes are not optional.

(Also remove warning about module-level global decl, because we can't
distinguish from code passed to exec.)

Define PyCompilerFlags type contains a single element,
cf_nested_scopes, that is true if a nested scopes future statement has
been entered at the interactive prompt.

New API functions:
    PyNode_CompileFlags()
    PyRun_InteractiveOneFlags()
    -- same as their non Flags counterparts except that the take an
       optional PyCompilerFlags pointer

compile.c: In jcompile() use PyCompilerFlags argument.  If
    cf_nested_scopes is true, compile code with nested scopes.  If it
    is false, but the code has a valid future nested scopes statement,
    set it to true.

pythonrun.c: Create a new PyCompilerFlags object in
    PyRun_InteractiveLoop() and thread it through to
    PyRun_InteractiveOneFlags().

symtable.h, so that they can be used by external module.

Improve error handling in symtable_enter_scope(), which return an
error code that went unchecked by most callers. XXX The error handling
in symtable code is sloppy in general.

Modify symtable to record the line number that begins each scope.
This can help to identify which code block is being referred to when
multiple blocks are bound to the same name.

Add st_scopes dict that is used to preserve scope info when
PyNode_CompileSymtable() is called.  Otherwise, this information is
tossed as soon as it is no longer needed.

Add Py_SymtableString() to pythonrun; analogous to Py_CompileString().

on Win64.

This closes bug http://sourceforge.net/bugs/?func=detailbug&group_id=5470&bug_id=116516

PyOS_setsig().

This should match the situation in the 1.6b1 tree.

PyRun_FileEx().  These are the same as their non-Ex counterparts but
have an extra argument, a flag telling them to close the file when
done.

Then this is used by Py_Main() and execfile() to close the file after
it is parsed but before it is executed.

Adding APIs seems strange given the feature freeze but it's the only
way I see to close the bug report without incompatible changes.

[ Bug #110616 ] source file stays open after parsing is done (PR#209)

couple of potential stack overflows, including bug #110615.

closes patch #101238