add debian packaging related information

Using the debian directory in this commit, it is possible to generate
libosmocore and libosmocore-dev packages (dpkgs).
diff --git a/debian/libosmocore-dbg.debhelper.log b/debian/libosmocore-dbg.debhelper.log
new file mode 100644
index 0000000..2742cb4
--- /dev/null
+++ b/debian/libosmocore-dbg.debhelper.log
@@ -0,0 +1,6 @@
+dh_auto_configure
+dh_auto_build
+dh_auto_test
+dh_prep
+dh_installdirs
+dh_auto_install