New GP evaluator release 2.4.1.compile-1

[Bill Allombert <allomber@math.u-bordeaux.fr>]

Hello PARI-dev,

I have made available a version of my latest GP evaluator:

<http://pari.math.u-bordeaux.fr/~bill/pari-2.4.1.compile-1.tar.gz>

This version uses a bytecode compiler and a bytecode evaluator.
For experimentation, two extra GP functions are included:
closure(cmd): return the closure associated to the GP command cmd.
disassemble(closure): disassemble the bytecode associated to a closure.

This version fixes all outstanding issues with the previous experimental
parser and is very close to be able to replace the original evaluator.

So now is the time to check if this version run your critical GP
scripts!

Known user-visible differences:

1) about five time faster.

2) uses much less system stack, thus allows for deeper recursion.

3) uses more PARI stack when reading objects.

4) Error messages are sometimes different, thought they are similar.

5) Functions added through install() must not be referenced before being
installed (for now).

6) ?func does not display space around the equal sign.

7) does not check for misuse of global variable and declaration of
the same local variable twice.

Cheers,
Bill.