extend "can_read" function. returns true, if no explicit filename is given, but just the extension.

closes #2431

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@1260 fdac6126-5c0c-442c-9429-916003d36597

src/OpenMesh/Core/IO/reader/BaseReader.hh

@@ -131,7 +131,11 @@ public:
                     Options& _opt) = 0;
 
 
-  /// Returns true if reader can parse _filename (checks extension)
+  /** \brief Returns true if writer can parse _filename (checks extension).
+   * _filename can also provide an extension without a name for a file e.g. _filename == "om" checks, if the reader can read the "om" extension
+   * @param _filename complete name of a file or just the extension
+   * @result true, if reader can read data with the given extension
+   */
   virtual bool can_u_read(const std::string& _filename) const;