configure.ac: support large-file for stat64

configure.ac: support large-file for stat64

dbus-daemon is not expected to open files with large *sizes*, but without
large file support, calling [f]stat() on a file that happens to have a
large inode number will fail with EOVERFLOW (see stat(2)). For example,
files mounted from an NFS server might have large inode numbers.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=93545
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
[smcv: shorten and clarify commit message; move AC_SYS_LARGEFILE
after AC_USE_SYSTEM_EXTENSIONS because nothing should compile C before
that point]
Reviewed-by: Simon McVittie <simon.mcvittie@collabora.co.uk>