STYLE: Remove useless install generator typedefs

The cmInstall*Generator classes all derive from cmInstallGenerator which
provides the Indent typedef so they do not need to provide it

Source/cmInstallDirectoryGenerator.h

@@ -35,7 +35,6 @@ public:
   virtual ~cmInstallDirectoryGenerator();
 
 protected:
-  typedef cmInstallGeneratorIndent Indent;
   virtual void GenerateScriptActions(std::ostream& os, Indent const& indent);
   std::vector<std::string> Directories;
   std::string FilePermissions;

Source/cmInstallExportGenerator.h

@@ -42,7 +42,6 @@ public:
 protected:
   typedef std::vector<cmTargetExport*> ExportSet;
 
-  typedef cmInstallGeneratorIndent Indent;
   virtual void GenerateScript(std::ostream& os);
   virtual void GenerateScriptConfigs(std::ostream& os, Indent const& indent);
   virtual void GenerateScriptActions(std::ostream& os, Indent const& indent);

Source/cmInstallFilesGenerator.h

@@ -35,7 +35,6 @@ public:
   virtual ~cmInstallFilesGenerator();
 
 protected:
-  typedef cmInstallGeneratorIndent Indent;
   virtual void GenerateScriptActions(std::ostream& os, Indent const& indent);
   std::vector<std::string> Files;
   bool Programs;

Source/cmInstallTargetGenerator.h

@@ -64,7 +64,6 @@ public:
   bool IsImportLibrary() const { return this->ImportLibrary; }
 
 protected:
-  typedef cmInstallGeneratorIndent Indent;
   virtual void GenerateScript(std::ostream& os);
   virtual void GenerateScriptConfigs(std::ostream& os, Indent const& indent);
   virtual void GenerateScriptActions(std::ostream& os, Indent const& indent);