Trac #25688: Inaccuracy in symbolic series result on 32bit Linux

From https://trac.sagemath.org/ticket/24838#comment:64

On 32-bit:
{{{
File "src/sage/functions/hypergeometric.py", line 148, in
sage.functions.hypergeometric
Failed example:
    hypergeometric_U(2, 2, x).series(x == 3, 100).subs(x=1).n()
Expected:
    0.403652637676806
Got:
    0.403651580752398
}}}

Pynac is not involved in the numerics (`hypergeometric_U` is not a
`GinacFunction`), so the hypothesis is that the expression before `.n()`
is different with 32bit Linux pynac-0.7.22.

URL: https://trac.sagemath.org/25688
Reported by: rws
Ticket author(s): Dave Morris
Reviewer(s): Matthias Koeppe

src/sage/functions/hypergeometric.py

@@ -145,7 +145,7 @@
 
     sage: hypergeometric_M(2, 2, x).series(x, 3)
     1 + 1*x + 1/2*x^2 + Order(x^3)
-    sage: hypergeometric_U(2, 2, x).series(x == 3, 100).subs(x=1).n() # known bug (see :trac:`25688`)
+    sage: hypergeometric_U(2, 2, x).series(x == 3, 100).subs(x=1).n()
     0.403652637676806
     sage: hypergeometric_U(2, 2, 1).n()
     0.403652637676806