debian: build manuals as osmo-remsim-doc package

Change-Id: If5812983d319a32864f5f34b160978533465d185
diff --git a/debian/osmo-remsim-doc.install b/debian/osmo-remsim-doc.install
new file mode 100644
index 0000000..e460a4d
--- /dev/null
+++ b/debian/osmo-remsim-doc.install
@@ -0,0 +1 @@
+usr/share/doc/osmo-remsim-doc/*.pdf