Update locale module of centos-art.sh script.
    
    - Previously, when processing docbook documents, a warning was printed
      when translatable strings were retrieved from docbook documents with
      relative paths inside. This update fixes this issue by adding the
      RENDER_TARGET variable to files function and moving inside it at the
      very moment of extracting translatable strings from such docbook
      files using xml2po command.
    
    - Previously, when producing PO files for shell scripts, the
      --copyright-holder option was used to print the copyright
      information in a comment on top of the file. When such a comment is
      present in a PO file, the file program fails to identify the PO file
      as such (e.g., it identifies it as text/plain instead of text/x-po).
      This update removed the --copyright-holder option from sh function
      in order for file program to recognize the PO file as such.