Added shell variable A2SERVER_SCRIPT_URL which allows you to replace
Ivan's server with another URL for development. If unset, scripts will
default to "http://appleii.ivanx.com/a2server/" as usual.
This will not allow you to use these scripts for development directly,
and in fact may have been over-zealous in removing hardcoded ivanx
links. Also, Ivan's webserver has a slightly different layout than this
repository because I haven't tried to make this an apache directory
structure full of mixed HTML, scripts, .htaccess files, etc.
This reflects Ivan Drucker's current A2SERVER scripts as of 2015-Oct-01,
version 1.24. These are unmodified and cannot be directly used yet. A
later patch will begin correcting that, but a baseline is important.
