closures for built-in GP functions

[Bill Allombert <Bill.Allombert@math.u-bordeaux1.fr>]

Hello PARI-dev,

I have committed a patch which allow to use built-in GP function as
closures:

? apply(sin,[1,2,3])
%1 = [0.84147098480789650665250232163029899962, 0.90929742682568169539601986591174484270, 0.14112000805986722210074480280811027985]
? select([1,2,3,4,5,6],isprime)
%2 = [2, 3, 5]

For backward compatibility this does not affect functions without
mandatory arguments.

Cheers,
Bill.