document that libraries have their own Debian packages

* NEWS, doc/org/install.org: Here.

NEWS

 New in spot 1.99.1a (not yet released)
 
-  * A missing Python.h is now diagnosied at ./configure time,
+  * A missing Python.h is now diagnosed at ./configure time,
     with the suggestion to either install python3-devel, or
     run ./configure --disable-python.
 
+  * Debian packages for libraries have been split from
+    the main Spot package, as per Debian guidelines.
+
   * Bugs fixed:
     - p[+][:*2] was not detected as belonging to siPSL
     - scc_filter() would incorrectly remove Fin marks from
       rejecting SCCs.
+    - the libspotltsmin library is installed
+
 
 New in spot 1.99.1 (2015-06-23)
 

doc/org/install.org

@@ -73,12 +73,14 @@ apt-get update
 apt-get install spot libspot-dev spot-doc python3-spot # Or a subset of those
 #+END_SRC
 
-The package =spot= contains the libraries and [[file:tools.org][command-line
-tools]]. =libspot-dev= contains the header files if you plan to use Spot
-in a C++11 program. =spot-doc= contains some html (including these
-pages) and pdf documentation. Finally =python3-spot= contains some
-Python bindings (this package also installs some ipython notebooks
-that you can use as examples).
+The package =spot= contains the [[file:tools.org][command-line tools]]. =libspot-dev=
+contains the header files if you plan to use Spot in a C++11
+program. =spot-doc= contains some html (including these pages) and pdf
+documentation. Finally =python3-spot= contains some Python bindings
+(this package also installs some ipython notebooks that you can use as
+examples).  The packages containing the libraries (=libspot0=,
+=libbddx0=, =libspotltsmin0=) are automatically installed as
+dependencies of the previous packages.
 
 These packages should work in a recent *Ubuntu* as well, provided you
 also add a path to a repository that distributes the GCC 4.9 runtime.
@@ -88,7 +90,6 @@ You can do that for instance with:
 add-apt-repository -y ppa:ubuntu-toolchain-r/test
 #+END_SRC
 
-
 * Installing from git
 
 The =master= branch of the git repository contains the code for the