Add README to comply with GNU maintainer manual.

diff --git a/lib/gsl-extras/README b/lib/gsl-extras/README
new file mode 100644 (file)
index 0000000..275bab1
--- /dev/null
+++ b/lib/gsl-extras/README
@@ -0,0 +1,3 @@
+The files in this directory are not part of GNU PSPP, but they are
+used with GNU PSPP.  In the future, they will likely become part of
+the GNU Scientific Library.