debian: fix some lintian warnings and errors

* debian/control: Update standars-version.  Add missing ${misc:Depends}.
Use Depends: ${source:Version} for libspot-dev.  Fix description of
spot.
* debian/spot-doc.doc-base: Move the doc to Science/Mathematics.

debian/control

@@ -3,7 +3,7 @@ Section: science
 Priority: optional
 Maintainer: Alexandre Duret-Lutz <adl@lrde.epita.fr>
 Build-Depends: debhelper (>= 9), python3-all-dev
-Standards-Version: 3.9.5
+Standards-Version: 3.9.6
 Homepage: http://spot.lip6.fr/
 
 Package: spot
@@ -12,7 +12,7 @@ Section: science
 Recommends: graphviz
 Suggests: libspot-dev, spot-doc, python3-spot
 Depends: ${shlibs:Depends}, ${misc:Depends}
-Description: Spot, a model checking library
+Description: model checking and omega-automata manipulation library
  Library and tools to manipulate omega-automata as well as
  linear-temporal logic (LTL & PSL).
 
@@ -20,15 +20,16 @@ Package: libspot-dev
 Architecture: all
 Section: libdevel
 Suggests: spot-doc
-Depends: spot (= ${binary:Version})
+Depends: spot (= ${source:Version}), ${misc:Depends}
 Description: headers for the Spot model checking library
  C++ headers for the Spot library.
 
 Package: spot-doc
 Section: doc
 Architecture: all
+Depends: ${misc:Depends}
 Description: documentation for Spot
- Developer documentation for Spot.
+ HTML and PDF documentation for Spot.
 
 Package: python3-spot
 Architecture: any

debian/spot-doc.doc-base

@@ -2,7 +2,7 @@ Document: spot
 Title: Spot documentation
 Author: Alexandre Duret-Lutz et al.
 Abstract: User documentation for Spot
-Section: science
+Section: Science/Mathematics
 
 Format: HTML
 Index: /usr/share/doc/spot/userdoc/tools.html