postgresql: fix pgac_cv_snprintf_long_long_int_modifier

Supplementary change the pgac_cv_snprintf_long_long_int_modifier from
complete format '%lld' to modifier 'll' version only (forgotten in commit
02c43157 ([1])).

Fixes Bug 9451 ([2]).

[1] https://git.buildroot.net/buildroot/commit/?id=02c43157ab09f6fe4078fd1145fc9d403d66c089
[2] https://bugs.busybox.net/show_bug.cgi?id=9451



Reported-by: Daniel <dde@innovaphone.com>
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>