debian: move libraries into separate packages

* debian/control (libbddx-dev, libbddx0, libspot0): New packages.
(libspot-dev): Make it "Architecture: any".
* debian/libspot-dev.install: Include the .so symlink.
* debian/spot.install: Remove the libraries.
* debian/libbddx-dev.install, debian/libbddx0.install,
debian/libspot0.install: New files.
* Makefile.am: Distribute them.

debian/libspot-dev.install

@@ -1 +1,2 @@
-usr/include
+usr/include/spot
+usr/lib/*-*/libspot.so