Do not raise an Invalid_argument exception is Sys.argv[0] is blank.

This can happen if the program is execed with a blank array.  In this
situation, Sys.executable_name will be blank and not raise an exception.
Sync CHANGES and correct some typos
fix typos in CHANGES and fix caps
Merge pull request #23 from avsm/blank-argv0-fix

Blank argv0 fix