Some patches in the GIT repository

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

Dear PARI developers,

I would like to anounce some patches that are available through the GIT browser:
<http://pari.math.u-bordeaux.fr/cgi-bin/gitweb.cgi?p=pari.git;a=summary>

1) bill-pari_err_to_GEN
This patch adds a function pari_err2GEN which convert a PARI error to a GEN object.
A function pari_err_display allows to convert the GEN object back to the error message.
Eventually we could add a new PARI type t_ERROR for such GEN objects (they are just t_VEC
currently). This would allow to pass PARI error around.

2) bill-runqueue_ellsea
This patch adds a new Configure option '--mt=pthread' which allows PARI to use POSIX threads
to parallellize some functions, through an abstract helper 'pari_run_queue'.
Only ellsea is parallellized in this patch. This works, but expect major changes.

3) bill-valgrind_stack_fixup, bill-valgrind_stack_check
These patches instrument the PARI stack allocation code so that the memory checker valgrind
can detect bad usage of the PARI stack. 

4) bill-polredbest
This patch add a function polredbest which returns the 'smallest' polynomial in the set
[P] union polred(P), where P is a integral polynomial. This is more usable than polred
and usually faster than polredabs.

Cheers,
Bill.