Go to +1 reference accounting.

The V routine now returns a new value with 1 reference count instead of 0.
I bubbled this through the whole program, and it makes things much more sure
and reliable.

Checking time stamps in build script again.  Added handy "fexl" script.

Removed internal check program test/run.c in factor of fexl-based test/a1.fxl.
You still use test/run and test/check though.

No more replacement inside forms during evaluation.  Evaluation is now purely
functional.  The '=' form of lambda definition does eager evaluation, and '=='
does lazy.

Added more built-in functions.  Reporting errors in a very slick way.

Among the new functions is put_to_error, which allows you to wrap a function so
that all its output goes to stderr.