[tex-live] source changes

[Karl Berry]

            This is extended TeX, Version 3.14159 (Web2C 7.3.7)

I guess it's too late, but how about

  This is TeX with extensions, Version 3.14159 (Web2C 7.3.7)

That seems like the most accurate statement -- TeX is still present, but
other things are present too.  Except for the -src-specials madness
which actually is not TeX.

My second favorite is:

        This is web2c-TeX, Version 3.14159 (Web2C 7.3.7)

Which also is at least descriptive of the situation and tells the user
what they're getting (although it's redundant :).