This change implements a new bytecode compiler, based on a
transformation of the parse tree to an abstract syntax defined in
Parser/Python.asdl.

The compiler implementation is not complete, but it is in stable
enough shape to run the entire test suite excepting two disabled
tests.

Don't output empty tags
Escape page header
Remove <p> before <table> (tidy complains)

too-mechanical translation when converting html() to text() (simply stripped
strong() where it appeared).

[Bug #758665] cgitb.scanvars() fails because of an unititialized value variable.  Patch from Robin Becker.

[Bugfix candidate] Escape traceback type and value.  There are probably additional cases where cgitb.py doesn't escape as paranoidly as it should (e.g. attribute names)

Weinberg).  This changes all uses of deprecated tempfile functions to
the recommended ones.

Don't show hidden fields of exception values (names starting with '_').

"handler()" function, not the "handle()" function.

By default, save sys.stdout in self.file when a Hook instance is created
    (e.g. when cgitb.enable() is called).

- file URL now starts with "file://" (standard) rather than "file:"
- new optional argument 'context' to enable()
- repeated variable names don't have their values shown twice
- dotted attributes are shown; missing attributes handled reasonably
- highlight the whole logical line even if it has multiple physical lines
- use nice generator interface to tokenize
- formatting fixed so that it looks good in lynx, links, and w3m too

A few enhancements are pending, but this should work reliably.