debian: Split the libraries into separate packages

This way one can install two ABI incompatible versions of the
library at the same time. This will ease future transition. Create
a dummy/compatible package.
diff --git a/debian/libosmotrau0.install b/debian/libosmotrau0.install
new file mode 100644
index 0000000..cef0740
--- /dev/null
+++ b/debian/libosmotrau0.install
@@ -0,0 +1 @@
+usr/lib/libosmotrau.so.*