Merge topic 'join-algorithm'

55a73e6b Use the cmJoin algorithm where possible.
8dc8d756 cmStandardIncludes: Add a join algorithm for string containers.
b5813cee cmInstallCommand: Remove unused variable.

Source/cmTargetIncludeDirectoriesCommand.cxx

@@ -91,15 +91,7 @@ void cmTargetIncludeDirectoriesCommand
 
   if (system)
     {
-    std::string joined;
-    std::string sep;
-    for(std::vector<std::string>::const_iterator it = content.begin();
-      it != content.end(); ++it)
-      {
-      joined += sep;
-      sep = ";";
-      joined += *it;
-      }
+    std::string joined = cmJoin(content, ";");
     tgt->AppendProperty("INTERFACE_SYSTEM_INCLUDE_DIRECTORIES",
                         joined.c_str());
     }