splint: improve meta attributes

- don't repeat package name in description
- prefer licenses.gpl2Plus over free form "GPLv2+" license name
- add platform attribute so that splint will be available in the channel

pkgs/development/tools/analysis/splint/default.nix

···
 
   doCheck = true;
 
-  meta = {
+  meta = with stdenv.lib; {
     homepage = http://splint.org/;
-    description = "Splint, an annotation-assisted lightweight static analyzer for C";
+    description = "Annotation-assisted lightweight static analyzer for C";
 
     longDescription = ''
       Splint is a tool for statically checking C programs for security
···
       checking than can be done by any standard lint.
     '';
 
-    license = "GPLv2+";
+    license = licenses.gpl2Plus;
+    platforms = platforms.linux;
   };
-}
+}