SystemTools: Accept strings in IsSubDirectory

The arguments are assumed to be non-null.

Change-Id: Ibe8e9fc9c932efc55cc18f0e06b2db61bc168817

SystemTools.cxx

@@ -4335,9 +4335,9 @@ kwsys_stl::string SystemTools::GetParentDirectory(const char* fileOrDir)
   return SystemTools::GetFilenamePath(fileOrDir);
 }
 
-bool SystemTools::IsSubDirectory(const char* cSubdir, const char* cDir)
+bool SystemTools::IsSubDirectory(const kwsys_stl::string& cSubdir, const kwsys_stl::string& cDir)
 {
-  if(!*cDir)
+  if(cDir.empty())
     {
     return false;
     }

SystemTools.hxx.in

@@ -487,7 +487,7 @@ public:
   /**
    * Check if the given file or directory is in subdirectory of dir
    */
-  static bool IsSubDirectory(const char* fileOrDir, const char* dir);
+  static bool IsSubDirectory(const kwsys_stl::string& fileOrDir, const kwsys_stl::string& dir);
 
   /** -----------------------------------------------------------------
    *               File Manipulation Routines