M config_defaults_inc.php

• Added document_files_prefix configuration option. This is the prefix of the
  file system names for files uploaded to projects.

M lang/strings_english.txt

• Removed $s_document_files_prefix since it is now a configuration option.

M proj_doc_add.php

• Changed to use the configuration option rather than the localised string. Otherwise
  depending on the user who uploaded the file, the prefix will be different.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2020 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9