Add copright headers and license files, list Pablo as author

The kernel module still only listed me as author, even though Pablo
was doing most of the work on it after my initial incomplete version.
diff --git a/AUTHORS b/AUTHORS
new file mode 100644
index 0000000..7deed5b
--- /dev/null
+++ b/AUTHORS
@@ -0,0 +1 @@
+Pablo Neira Ayuso <pablo@gnumonks.org>