[Distutils] Make ez_setup.py/easy_install $PATH aware

[Ben Bangert]

This is hopefully a pretty minor fix, and now that I think about it,  
I'm surprised it hasn't been in setuptools for ages. Some platforms  
don't have something setup right so that Python scripts are installed  
deep into Python library directories that definitely aren't in the  
$PATH.

It becomes embarrassing as one tries to write "Install" instructions,  
and has to keep including a "Do you have any idea where the XXX  
command is? Try finding it and adding that dir to your path". Or  
having to tell people not to do anything without making a  
~/.pydistutils.cfg file with a install-dir location.

So.... couldn't ez_setup.py look at the $PATH present, and notice  
when the install location is outside of it? Then it could either give  
a nice big warning about how the scripts its about to install aren't  
going to be available without re-installing with the package and  
defining a install-dir for scripts, or adding the path to your $PATH.  
Surely there ought to be a better solution than blindly copying  
scripts into locations that will leave users wondering why they can't  
be run, and it seems like the system for that should be in  
ez_setup.py as thats a first step to getting the whole setuptools/ 
easy_install system going.

Thanks,
Ben