Export: Generate INTERFACE_LINK_LIBRARIES property on targets.

This property is generated only for targets which have recorded
policy CMP0022 as NEW, and a compatibility mode is added to
additionally export the old interfaces in that case too.

If the old interfaces are not exported, the generated export files
require CMake 2.8.12. Because the unit tests use a version which
is not yet called 2.8.12, temporarily require a lower version.

Source/cmInstallExportGenerator.h

@@ -31,7 +31,7 @@ public:
                            const std::vector<std::string>& configurations,
                            const char* component,
                            const char* filename, const char* name_space,
-                           cmMakefile* mf);
+                           bool exportOld, cmMakefile* mf);
   ~cmInstallExportGenerator();
 
   cmExportSet* GetExportSet() {return this->ExportSet;}
@@ -52,6 +52,7 @@ protected:
   std::string FilePermissions;
   std::string FileName;
   std::string Namespace;
+  bool ExportOld;
   cmMakefile* Makefile;
 
   std::string TempDir;