Avoid multiple copies of AC_GNU_SOURCE in the configure file.
[pspp] / config /
drwxr-xr-x   ..
-rw-r--r-- 13029 ChangeLog
-rwxr-xr-x 4455 srclist-update
-rw-r--r-- 10154 srclist.txt
-rw-r--r-- 1018 srclistvars.sh