lang0 release

This is an update to my previous perl server with the following:

• Added Python, so calls to Python libraries can now be made in addition to Perl.
• The Perl and Python servers now generate an Arc literal expression for their return value. This makes it easy to return specific Arc values such as symbols.
• Errors raised in the Perl or Python code now print a traceback and raise an error back in Arc.
• The Perl or Python server is now automatically started when the first call to perl or python is made.

Documentation is at lang and a discussion of the particular design decisions is at lang-faq.