added shortest ext function

Source/cmSystemTools.cxx

@@ -1247,6 +1247,23 @@ std::string cmSystemTools::GetFilenameExtension(const std::string& filename)
     }
 }
 
+/**
+ * Return file extension of a full filename (dot included).
+ */
+std::string cmSystemTools::GetFilenameShortestExtension(const std::string& filename)
+{
+  std::string name = cmSystemTools::GetFilenameName(filename);
+  std::string::size_type dot_pos = name.rfind(".");
+  if(dot_pos != std::string::npos)
+    {
+    return name.substr(dot_pos);
+    }
+  else
+    {
+    return "";
+    }
+}
+
 
 /**
  * Return file name without extension of a full filename (i.e. without path).

Source/cmSystemTools.h

@@ -242,6 +242,7 @@ public:
   
   ///! return file extension of a full filename (dot included).
   static std::string GetFilenameExtension(const std::string&);
+  static std::string GetFilenameShortestExtension(const std::string&);
   
   ///! return file name without extension of a full filename.
   static std::string GetFilenameNameWithoutExtension(const std::string&);