defaults change new_galois_format and simplify

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

Dear PARI dev,

We plan to switch the two defaults 
new_galois_format (from 0 to 1)
and 
simplify from (1 to 0)
for the next stable release.

Users will be able to switch them back in the .gprc with
new_galois_format = 0
simplify = 1

Setting simplify to 0 avoid surprises:

? \y1
? a = Mod(y,y^2-2); P = lift((x-a)*(x+a))
%1 = x^2 - 2
? polgalois(%)
%2 = [2,-1,1,"S2"]
? polgalois(P)
  ***   at top-level: polgalois(P)
  ***                 ^------------
  *** polgalois: incorrect type in galois [not in Z[X]] (t_POL).

Just call simplify() explicitly when needed.
a = Mod(y,y^2-2); P = simplify(lift((x-a)*(x+a)))

Cheers,
Bill.